Prioritizing highly compressed traffic to provide a predetermined quality of service

ABSTRACT

A network optimization engine can be used to optimize the transmission of network traffic by employing means to prioritize highly compressed network traffic over other network traffic. The network optimization engine accomplishes network traffic optimization by calculating a compression ratio for received data packets and determining whether the calculated compression ratios exceed a compression ratio threshold. The predetermined compression ratio threshold can be a hard coded value or an empirically determined compression ratio threshold that is calculated using a sample of the received network packets. Network packets having a compression ratio that exceeds the compression ratio threshold are classified as highly compressed network traffic and transmitted according to a transmission scheme that is different than a transmission scheme used to transmit non-highly compressed network traffic.

RELATED APPLICATIONS

This Patent Application claims priority to U.S. Provisional PatentApplication No. 61/501,739, filed on Jun. 27, 2011, and U.S. ProvisionalPatent Application No. 61/501,695, filed on Jun. 27, 2011, thedisclosures of which are considered part of the disclosure of thisapplication and are herein incorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The disclosure generally relates to network optimization. In particular,the disclosure describes methods and systems for prioritizing a segmentof network traffic to increase the probability of providing a guaranteedquality of service for that segment of network traffic.

BACKGROUND OF THE DISCLOSURE

Wide Area Network (WAN) optimization solutions are often used toaccelerate the transmission of data over a network. The poor performanceand IT complexity associated with computing systems that span WANs canbe mitigated through optimization schemes which reduce the amount ofdata transmitted from one system end point to another. Traditionally,using a network-centric approach to WAN optimization can allowenterprises to consolidate their IT infrastructure in private clouds,public clouds or a branch office.

Enterprises now support many different types of end-user devices overdistributed links such as the internet. Furthermore, enterprises oftendeliver applications and services, e.g. voice-over-IP (VOIP), 3Dgraphics applications and Office, over these distributed links. It isnow common for users to be decoupled from their applications such thatapplications and services are delivered to end-users from any networknode. This form of distributed computing requires data delivery overmultiple different types of networks using any number of communicationprotocols. Optimizing WANs in this environment can be difficult becausethe network landscape is often unknown and can change. One method foroptimizing WANs includes reducing the size of a network pipe. While thismethod can reduce the amount of bandwidth used during a datatransmission, there is still little control over how the availablebandwidth is distributed to new or parallel data transmissions. Thismethod also does not provide IT departments with a way to controlnetwork parameters that can affect end-user experience and mitigate thedamage done by users who use an excessive amount of bandwidth.

Optimizing a WAN such that critical applications and services aredelivered in a minimal amount of time using an optimal amount ofbandwidth can require a user-centric approach to optimization. Thus,systems and methods are needed to provide user-centric optimizationrather than network-centric optimization.

In some instances, WAN optimization can be accomplished by using trafficshaping to provide a quality of service to the optimized WAN traffic.Traffic shaping ensures support for link-sharing of integrated serviceswhich allows resource sharing among applications that require differentnetwork services but belong to the same administrative class. Networktraffic can contain multiple service classes such that some datacorresponds to real-time service requirements while others correspond toother classes of service. In some instances, data packets correspondingto different sessions or belonging to different classes of serviceinteract with each other by using the same output link of an appliance.This appliance can be a switch, router, gateway or other devicesometimes referred to as a WAN pipe. The scheduling algorithm at theswitching nodes can play a critical role in substantially simultaneouslysupporting link-sharing, real-time traffic management and best-efforttraffic management.

Traffic shaping can include minimizing an amount of data transmittedacross a network and transmitting the data according to a method thatensures bursty traffic conforms to the system's defined flow limits. Anend-to-end traffic management algorithm can be used to estimatebandwidth usage and distribute available bandwidth among managedsessions. Distributing bandwidth fairly among competing sessions caninclude using an algorithm that does the following: provides thetightest delay bound among all fair queuing algorithms; has the smallestworst-case fair index amongst all fair queuing algorithms; and has arelatively low implementation complexity. Improving such an algorithmcan include optimizing portions of the algorithm so that the performanceof the algorithm surpasses other hierarchical fair service algorithms.

Thus, systems and methods are needed to provide an optimizedhierarchical fair service algorithm that creates levels of prioritywithin delay-sensitive traffic and fairness among the data flows withinthose priorities. Further, systems and methods are needed that mitigatethe problems posed by low priority DBC traffic (or other highlycompressed traffic) that must retain an enormous amount of memory untila highly compressed packet is acknowledged. Retaining this informationcan be required because it may necessary to retransmit the highlycompressed traffic should the traffic be lost on a WAN.

BRIEF SUMMARY OF THE DISCLOSURE

Described herein are aspects of methods and systems for optimizing thetransmission of network traffic over a network by applying a particularquality of service (“QoS”) to a segment of network traffic identified ashighly compressed traffic. Applying a different QoS to highly compressednetwork traffic can reduce the amount of memory needed to transmithighly compressed traffic thereby increasing the amount of memoryavailable to process non-highly compressed traffic. This optimizationresults in a more efficient transmission of network traffic with minimaldelay and allows a network optimization engine to output a greateramount of uncompressed traffic.

This disclosure describes methods and systems for optimizing networktraffic transmission using a network optimization engine that executeson an appliance to receive data packets that are transmitted over anetwork. The network optimization engine analyzes each of the receiveddata packets and calculates a compression ratio for the received datapackets. Upon calculating the compression ratios, the trafficoptimization determines whether each data packet's compression ratioexceeds a predetermined compression ratio threshold. Those received datapackets that have a compression ratio that exceeds the predeterminedcompression ratio threshold are classified as highly compressed traffic.The network optimization engine sorts the received data packetsaccording to whether a data packet has a highly compressed trafficclassification and transmits those data packets classified as highlycompressed traffic according to a first transmission scheme. The networkoptimization engine then transmits those data packets that were notclassified as highly compressed traffic according to a secondtransmission scheme that is different from the first transmissionscheme.

In one aspect the network optimization engine receives data packets froma common output link which can include either a common router or acommon switch. In some embodiments, the network optimization enginereceives data packets transmitted over a wide area network (WAN) pipe.

The network optimization engine can calculate the predeterminedcompression ratio threshold by calculating a compression ratio for aportion of the received data packets, averaging the calculatedcompression ratios to determine an average compression ratio, anddesignating the average compression ratio as the predeterminedcompression ratio threshold. In some embodiments, the portion of thereceived data packets can include data packets generated by a firstapplication.

In some embodiments, the network optimization engine can classify datapackets as highly compressed traffic by marking the data packets as partof a highly compressed traffic class. In other embodiments, the networkoptimization engine classifies the data packets by modifying one or morecharacteristics of a QoS parameter of the data packets.

The network optimization engine can declassify data packets as highlycompressed traffic by determining, subsequent to receiving data packets,whether the received data packets include a traffic class marking thatindicates that the data packets belong to the highly compressed trafficclass. After identifying a portion of the received data packets as partof the highly compressed traffic class, the network optimization enginecan analyze the received data packet to calculate a compression ratiofor each data packet and further determine whether this calculatedcompression ratio falls below the predetermined compression ratiothreshold. When a data packet's compression ratio falls below thethreshold, the network optimization engine can remove that data packetfrom the highly compressed traffic class by modifying the data packet toremove any highly compressed traffic class markings.

In some embodiments, the network optimization engine can further orderthe sorted data packets according to timestamp values associated witheach data packet. Thus when the network optimization engine transmitsthe data packets, the network optimization engine can transmit the datapackets in a first-in-first-out order and according to the assignedtransmission scheme.

BRIEF DESCRIPTION OF THE FIGURES

The following figures depict certain illustrative embodiments of themethods and systems described herein, where like reference numeralsrefer to like elements. Each depicted embodiment is illustrative ofthese methods and systems and not limiting.

FIG. 1A is a block diagram of an embodiment of a network environment fora client to access a server via one or more network optimizationappliances.

FIG. 1B is a block diagram of another embodiment of a networkenvironment for a client to access a server via one or more networkoptimization appliances in conjunction with other network appliances.

FIG. 1C is a block diagram of another embodiment of a networkenvironment for a client to access a server via a single networkoptimization appliance deployed stand-alone or in conjunction with othernetwork appliances.

FIGS. 1D and 1E are block diagrams of embodiments of a computing device.

FIG. 2A is a block diagram of an embodiment of an appliance forprocessing communications between a client and a server.

FIG. 2B is a block diagram of another embodiment of a client and/orserver deploying the network optimization features of the appliance.

FIG. 3 is a block diagram of an embodiment of a client for communicatingwith a server using the network optimization feature.

FIG. 4A is a block diagram of an embodiment of a system for providingmulti-level classification of a network packet.

FIG. 4B is a block diagram of an embodiment of a network optimizationengine for providing multi-level classification of a network packet.

FIG. 5 is a block diagram of an embodiment of parent-child relationshipsof a plurality of layer 3-7 protocols.

FIG. 6 is a block diagram of an embodiment of a network optimizationsystem.

FIG. 7 is a flow chart of an embodiment of a method for prioritizinghighly compressed traffic.

FIG. 8 is a flow chart of an embodiment of a method for prioritizingclasses of network traffic.

DETAILED DESCRIPTION OF THE DISCLOSURE

For purposes of reading the following description, the following outlineof the sections of the specification and their respective contents maybe helpful:

Section A: Network and Computing environment;

Section B: System and Appliance Architecture for Accelerating Deliveryof a Computing Environment to a Remote User;

Section C: Client Agent for Accelerating Communications Between a Clientand a Server;

Section D: Systems and Methods for Classifying Network Packets; and

Section E: Prioritizing Highly Compressed Traffic and Traffic Assignedto a Particular Traffic Class.

A. Network and Computing Environment

Prior to discussing the specifics of embodiments of the systems andmethods of an appliance and/or client, it may be helpful to discuss thenetwork and computing environments in which such embodiments may bedeployed. Referring now to FIG. 1A, an embodiment of a networkenvironment is depicted. In brief overview, the network environment hasone or more clients 102 a-102 n (also generally referred to as localmachine(s) 102, or client(s) 102) in communication with one or moreservers 106 a-106 n (also generally referred to as server(s) 106, orremote machine(s) 106) via one or more networks 104, 104′, 104″. In someembodiments, a client 102 communicates with a server 106 via one or morenetwork optimization appliances 200, 200′ (generally referred to asappliance 200). In one embodiment, the network optimization appliance200 is designed, configured or adapted to optimize Wide Area Network(WAN) network traffic. In some embodiments, a first appliance 200 worksin conjunction or cooperation with a second appliance 200′ to optimizenetwork traffic. For example, a first appliance 200 may be locatedbetween a branch office and a WAN connection while the second appliance200′ is located between the WAN and a corporate Local Area Network(LAN). The appliances 200 and 200′ may work together to optimize the WANrelated network traffic between a client in the branch office and aserver on the corporate LAN

Although FIG. 1A shows a network 104, network 104′ and network 104″(generally referred to as network(s) 104) between the clients 102 andthe servers 106, the clients 102 and the servers 106 may be on the samenetwork 104. The networks 104, 104′, 104″ can be the same type ofnetwork or different types of networks. The network 104 can be alocal-area network (LAN), such as a company Intranet, a metropolitanarea network (MAN), or a wide area network (WAN), such as the Internetor the World Wide Web. The networks 104, 104′, 104″ can be a private orpublic network. In one embodiment, network 104′ or network 104″ may be aprivate network and network 104 may be a public network. In someembodiments, network 104 may be a private network and network 104′and/or network 104″ a public network. In another embodiment, networks104, 104′, 104″ may be private networks. In some embodiments, clients102 may be located at a branch office of a corporate enterprisecommunicating via a WAN connection over the network 104 to the servers106 located on a corporate LAN in a corporate data center.

The network 104 may be any type and/or form of network and may includeany of the following: a point to point network, a broadcast network, awide area network, a local area network, a telecommunications network, adata communication network, a computer network, an ATM (AsynchronousTransfer Mode) network, a SONET (Synchronous Optical Network) network, aSDH (Synchronous Digital Hierarchy) network, a wireless network and awireline network. In some embodiments, the network 104 may comprise awireless link, such as an infrared channel or satellite band. Thetopology of the network 104 may be a bus, star, or ring networktopology. The network 104 and network topology may be of any suchnetwork or network topology as known to those ordinarily skilled in theart capable of supporting the operations described herein.

As depicted in FIG. 1A, a first network optimization appliance 200 isshown between networks 104 and 104′ and a second network optimizationappliance 200′ is also between networks 104′ and 104″. In someembodiments, the appliance 200 may be located on network 104. Forexample, a corporate enterprise may deploy an appliance 200 at thebranch office. In other embodiments, the appliance 200 may be located onnetwork 104′. In some embodiments, the appliance 200′ may be located onnetwork 104′ or network 104″. For example, an appliance 200 may belocated at a corporate data center. In one embodiment, the appliance 200and 200′ are on the same network. In another embodiment, the appliance200 and 200′ are on different networks.

In one embodiment, the appliance 200 is a device for accelerating,optimizing or otherwise improving the performance, operation, or qualityof service of any type and form of network traffic. In some embodiments,the appliance 200 is a performance enhancing proxy. In otherembodiments, the appliance 200 is any type and form of WAN optimizationor acceleration device, sometimes also referred to as a WAN optimizationcontroller. In one embodiment, the appliance 200 is any of the productembodiments referred to as WANScaler manufactured by Citrix Systems,Inc. of Ft. Lauderdale, Fla. In other embodiments, the appliance 200includes any of the product embodiments referred to as BIG-IP linkcontroller and WANjet manufactured by F5 Networks, Inc. of Seattle,Wash. In another embodiment, the appliance 200 includes any of the WXand WXC WAN acceleration device platforms manufactured by JuniperNetworks, Inc. of Sunnyvale, Calif. In some embodiments, the appliance200 includes any of the steelhead line of WAN optimization appliancesmanufactured by Riverbed Technology of San Francisco, Calif. In otherembodiments, the appliance 200 includes any of the WAN related devicesmanufactured by Expand Networks Inc. of Roseland, N.J. In oneembodiment, the appliance 200 includes any of the WAN related appliancesmanufactured by Packeteer Inc. of Cupertino, Calif., such as thePacketShaper, iShared, and SkyX product embodiments provided byPacketeer. In yet another embodiment, the appliance 200 includes any WANrelated appliances and/or software manufactured by Cisco Systems, Inc.of San Jose, Calif., such as the Cisco Wide Area Network ApplicationServices software and network modules, and Wide Area Network engineappliances.

In some embodiments, the appliance 200 provides application and dataacceleration services for branch-office or remote offices. In oneembodiment, the appliance 200 includes optimization of Wide Area FileServices (WAFS). In another embodiment, the appliance 200 acceleratesthe delivery of files, such as via the Common Internet File System(CIFS) protocol. In other embodiments, the appliance 200 providescaching in memory and/or storage to accelerate delivery of applicationsand data. In one embodiment, the appliance 205 provides compression ofnetwork traffic at any level of the network stack or at any protocol ornetwork layer. In another embodiment, the appliance 200 providestransport layer protocol optimizations, flow control, performanceenhancements or modifications and/or management to accelerate deliveryof applications and data over a WAN connection. For example, in oneembodiment, the appliance 200 provides Transport Control Protocol (TCP)optimizations. In other embodiments, the appliance 200 providesoptimizations, flow control, performance enhancements or modificationsand/or management for any session or application layer protocol. Furtherdetails of the optimization techniques, operations and architecture ofthe appliance 200 are discussed below in Section B.

Still referring to FIG. 1A, the network environment may includemultiple, logically-grouped servers 106. In these embodiments, thelogical group of servers may be referred to as a server farm 38. In someof these embodiments, the serves 106 may be geographically dispersed. Insome cases, a farm 38 may be administered as a single entity. In otherembodiments, the server farm 38 comprises a plurality of server farms38. In one embodiment, the server farm executes one or more applicationson behalf of one or more clients 102.

The servers 106 within each farm 38 can be heterogeneous. One or more ofthe servers 106 can operate according to one type of operating systemplatform (e.g., WINDOWS NT, manufactured by Microsoft Corp. of Redmond,Wash.), while one or more of the other servers 106 can operate onaccording to another type of operating system platform (e.g., Unix orLinux). The servers 106 of each farm 38 do not need to be physicallyproximate to another server 106 in the same farm 38. Thus, the group ofservers 106 logically grouped as a farm 38 may be interconnected using awide-area network (WAN) connection or metropolitan-area network (MAN)connection. For example, a farm 38 may include servers 106 physicallylocated in different continents or different regions of a continent,country, state, city, campus, or room. Data transmission speeds betweenservers 106 in the farm 38 can be increased if the servers 106 areconnected using a local-area network (LAN) connection or some form ofdirect connection.

Servers 106 may be referred to as a file server, application server, webserver, proxy server, or gateway server. In some embodiments, a server106 may have the capacity to function as either an application server oras a master application server. In one embodiment, a server 106 mayinclude an Active Directory. The client 102 may also be referred to asclient nodes or endpoints. In some embodiments, a client 102 has thecapacity to function as both a client node seeking access toapplications on a server and as an application server providing accessto hosted applications for other clients 102 a-102 n.

In some embodiments, a client 102 communicates with a server 106. In oneembodiment, the client 102 communicates directly with one of the servers106 in a farm 38. In another embodiment, the client 102 executes aprogram neighborhood application to communicate with a server 106 in afarm 38. In still another embodiment, the server 106 provides thefunctionality of a master node. In some embodiments, the client 102communicates with the server 106 in the farm 38 through a network 104.Over the network 104, the client 102 can, for example, request executionof various applications hosted by the servers 106 a-106 n in the farm 38and receive output of the results of the application execution fordisplay. In some embodiments, only the master node provides thefunctionality required to identify and provide address informationassociated with a server 106′ hosting a requested application.

In one embodiment, the server 106 provides functionality of a webserver. In another embodiment, the server 106 a receives requests fromthe client 102, forwards the requests to a second server 106 b andresponds to the request by the client 102 with a response to the requestfrom the server 106 b. In still another embodiment, the server 106acquires an enumeration of applications available to the client 102 andaddress information associated with a server 106 hosting an applicationidentified by the enumeration of applications. In yet anotherembodiment, the server 106 presents the response to the request to theclient 102 using a web interface. In one embodiment, the client 102communicates directly with the server 106 to access the identifiedapplication. In another embodiment, the client 102 receives applicationoutput data, such as display data, generated by an execution of theidentified application on the server 106.

Deployed with Other Appliances.

Referring now to FIG. 1B, another embodiment of a network environment isdepicted in which the network optimization appliance 200 is deployedwith one or more other appliances 205, 205′ (generally referred to asappliance 205 or second appliance 205) such as a gateway, firewall oracceleration appliance. For example, in one embodiment, the appliance205 is a firewall or security appliance while appliance 205′ is a LANacceleration device. In some embodiments, a client 102 may communicateto a server 106 via one or more of the first appliances 200 and one ormore second appliances 205.

One or more appliances 200 and 205 may be located at any point in thenetwork or network communications path between a client 102 and a server106. In some embodiments, a second appliance 205 may be located on thesame network 104 as the first appliance 200. In other embodiments, thesecond appliance 205 may be located on a different network 104 as thefirst appliance 200. In yet another embodiment, a first appliance 200and second appliance 205 is on the same network, for example network104, while the first appliance 200′ and second appliance 205′ is on thesame network, such as network 104″.

In one embodiment, the second appliance 205 includes any type and formof transport control protocol or transport later terminating device,such as a gateway or firewall device. In one embodiment, the appliance205 terminates the transport control protocol by establishing a firsttransport control protocol connection with the client and a secondtransport control connection with the second appliance or server. Inanother embodiment, the appliance 205 terminates the transport controlprotocol by changing, managing or controlling the behavior of thetransport control protocol connection between the client and the serveror second appliance. For example, the appliance 205 may change, queue,forward or transmit network packets in manner to effectively terminatethe transport control protocol connection or to act or simulate asterminating the connection.

In some embodiments, the second appliance 205 is a performance enhancingproxy. In one embodiment, the appliance 205 provides a virtual privatenetwork (VPN) connection. In some embodiments, the appliance 205provides a Secure Socket Layer VPN (SSL VPN) connection. In otherembodiments, the appliance 205 provides an IPsec (Internet ProtocolSecurity) based VPN connection. In some embodiments, the appliance 205provides any one or more of the following functionality: compression,acceleration, load-balancing, switching/routing, caching, and TransportControl Protocol (TCP) acceleration.

In one embodiment, the appliance 205 is any of the product embodimentsreferred to as Access Gateway, Application Firewall, ApplicationGateway, or NetScaler manufactured by Citrix Systems, Inc. of Ft.Lauderdale, Fla. As such, in some embodiments, the appliance 205includes any logic, functions, rules, or operations to perform servicesor functionality such as SSL VPN connectivity, SSL offloading,switching/load balancing, Domain Name Service resolution, LANacceleration and an application firewall.

In some embodiments, the appliance 205 provides a SSL VPN connectionbetween a client 102 and a server 106. For example, a client 102 on afirst network 104 requests to establish a connection to a server 106 ona second network 104′. In some embodiments, the second network 104″ isnot routable from the first network 104. In other embodiments, theclient 102 is on a public network 104 and the server 106 is on a privatenetwork 104′, such as a corporate network. In one embodiment, a clientagent intercepts communications of the client 102 on the first network104, encrypts the communications, and transmits the communications via afirst transport layer connection to the appliance 205. The appliance 205associates the first transport layer connection on the first network 104to a second transport layer connection to the server 106 on the secondnetwork 104. The appliance 205 receives the intercepted communicationfrom the client agent, decrypts the communications, and transmits thecommunication to the server 106 on the second network 104 via the secondtransport layer connection. The second transport layer connection may bea pooled transport layer connection. In one embodiment, the appliance205 provides an end-to-end secure transport layer connection for theclient 102 between the two networks 104, 104′.

In one embodiments, the appliance 205 hosts an intranet internetprotocol or intranetIP address of the client 102 on the virtual privatenetwork 104. The client 102 has a local network identifier, such as aninternet protocol (IP) address and/or host name on the first network104. When connected to the second network 104′ via the appliance 205,the appliance 205 establishes, assigns or otherwise provides anIntranetIP, which is network identifier, such as IP address and/or hostname, for the client 102 on the second network 104′. The appliance 205listens for and receives on the second or private network 104′ for anycommunications directed towards the client 102 using the client'sestablished IntranetIP. In one embodiment, the appliance 205 acts as oron behalf of the client 102 on the second private network 104.

In some embodiment, the appliance 205 has an encryption engine providinglogic, business rules, functions or operations for handling theprocessing of any security related protocol, such as SSL or TLS, or anyfunction related thereto. For example, the encryption engine encryptsand decrypts network packets, or any portion thereof, communicated viathe appliance 205. The encryption engine may also setup or establish SSLor TLS connections on behalf of the client 102 a-102 n, server 106 a-106n, or appliance 200, 205. As such, the encryption engine providesoffloading and acceleration of SSL processing. In one embodiment, theencryption engine uses a tunneling protocol to provide a virtual privatenetwork between a client 102 a-102 n and a server 106 a-106 n. In someembodiments, the encryption engine uses an encryption processor. Inother embodiments, the encryption engine includes executableinstructions running on an encryption processor.

In some embodiments, the appliance 205 provides one or more of thefollowing acceleration techniques to communications between the client102 and server 106: 1) compression, 2) decompression, 3) TransmissionControl Protocol pooling, 4) Transmission Control Protocol multiplexing,5) Transmission Control Protocol buffering, and 6) caching.

In one embodiment, the appliance 200 relieves servers 106 of much of theprocessing load caused by repeatedly opening and closing transportlayers connections to clients 102 by opening one or more transport layerconnections with each server 106 and maintaining these connections toallow repeated data accesses by clients via the Internet. This techniqueis referred to herein as “connection pooling”.

In some embodiments, in order to seamlessly splice communications from aclient 102 to a server 106 via a pooled transport layer connection, theappliance 205 translates or multiplexes communications by modifyingsequence number and acknowledgment numbers at the transport layerprotocol level. This is referred to as “connection multiplexing”. Insome embodiments, no application layer protocol interaction is required.For example, in the case of an in-bound packet (that is, a packetreceived from a client 102), the source network address of the packet ischanged to that of an output port of appliance 205, and the destinationnetwork address is changed to that of the intended server. In the caseof an outbound packet (that is, one received from a server 106), thesource network address is changed from that of the server 106 to that ofan output port of appliance 205 and the destination address is changedfrom that of appliance 205 to that of the requesting client 102. Thesequence numbers and acknowledgment numbers of the packet are alsotranslated to sequence numbers and acknowledgement expected by theclient 102 on the appliance's 205 transport layer connection to theclient 102. In some embodiments, the packet checksum of the transportlayer protocol is recalculated to account for these translations.

In another embodiment, the appliance 205 provides switching orload-balancing functionality for communications between the client 102and server 106. In some embodiments, the appliance 205 distributestraffic and directs client requests to a server 106 based on layer 4payload or application-layer request data. In one embodiment, althoughthe network layer or layer 2 of the network packet identifies adestination server 106, the appliance 205 determines the server 106 todistribute the network packet by application information and datacarried as payload of the transport layer packet. In one embodiment, ahealth monitoring program of the appliance 205 monitors the health ofservers to determine the server 106 for which to distribute a client'srequest. In some embodiments, if the appliance 205 detects a server 106is not available or has a load over a predetermined threshold, theappliance 205 can direct or distribute client requests to another server106.

In some embodiments, the appliance 205 acts as a Domain Name Service(DNS) resolver or otherwise provides resolution of a DNS request fromclients 102. In some embodiments, the appliance intercepts' a DNSrequest transmitted by the client 102. In one embodiment, the appliance205 responds to a client's DNS request with an IP address of or hostedby the appliance 205. In this embodiment, the client 102 transmitsnetwork communication for the domain name to the appliance 200. Inanother embodiment, the appliance 200 responds to a client's DNS requestwith an IP address of or hosted by a second appliance 200′. In someembodiments, the appliance 205 responds to a client's DNS request withan IP address of a server 106 determined by the appliance 200.

In yet another embodiment, the appliance 205 provides applicationfirewall functionality for communications between the client 102 andserver 106. In one embodiment, a policy engine 295′ provides rules fordetecting and blocking illegitimate requests. In some embodiments, theapplication firewall protects against denial of service (DoS) attacks.In other embodiments, the appliance inspects the content of interceptedrequests to identify and block application-based attacks. In someembodiments, the rules/policy engine includes one or more applicationfirewall or security control policies for providing protections againstvarious classes and types of web or Internet based vulnerabilities, suchas one or more of the following: 1) buffer overflow, 2) CGI-BINparameter manipulation, 3) form/hidden field manipulation, 4) forcefulbrowsing, 5) cookie or session poisoning, 6) broken access control list(ACLs) or weak passwords, 7) cross-site scripting (XSS), 8) commandinjection, 9) SQL injection, 10) error triggering sensitive informationleak, 11) insecure use of cryptography, 12) server misconfiguration, 13)back doors and debug options, 14) website defacement, 15) platform oroperating systems vulnerabilities, and 16) zero-day exploits. In anembodiment, the application firewall of the appliance provides HTML formfield protection in the form of inspecting or analyzing the networkcommunication for one or more of the following: 1) required fields arereturned, 2) no added field allowed, 3) read-only and hidden fieldenforcement, 4) drop-down list and radio button field conformance, and5) form-field max-length enforcement. In some embodiments, theapplication firewall of the appliance 205 ensures cookies are notmodified. In other embodiments, the appliance 205 protects againstforceful browsing by enforcing legal URLs.

In still yet other embodiments, the application firewall appliance 205protects any confidential information contained in the networkcommunication. The appliance 205 may inspect or analyze any networkcommunication in accordance with the rules or polices of the policyengine to identify any confidential information in any field of thenetwork packet. In some embodiments, the application firewall identifiesin the network communication one or more occurrences of a credit cardnumber, password, social security number, name, patient code, contactinformation, and age. The encoded portion of the network communicationmay include these occurrences or the confidential information. Based onthese occurrences, in one embodiment, the application firewall may takea policy action on the network communication, such as preventtransmission of the network communication. In another embodiment, theapplication firewall may rewrite, remove or otherwise mask suchidentified occurrence or confidential information.

Although generally referred to as a network optimization or firstappliance 200 and a second appliance 205, the first appliance 200 andsecond appliance 205 may be the same type and form of appliance. In oneembodiment, the second appliance 205 may perform the same functionality,or portion thereof, as the first appliance 200, and vice-versa. Forexample, the first appliance 200 and second appliance 205 may bothprovide acceleration techniques. In one embodiment, the first appliancemay perform LAN acceleration while the second appliance performs WANacceleration, or vice-versa. In another example, the first appliance 200may also be a transport control protocol terminating device as with thesecond appliance 205. Furthermore, although appliances 200 and 205 areshown as separate devices on the network, the appliance 200 and/or 205could be a part of any client 102 or server 106.

Referring now to FIG. 1C, other embodiments of a network environment fordeploying the appliance 200 are depicted. In another embodiment asdepicted on the top of FIG. 1C, the appliance 200 may be deployed as asingle appliance or single proxy on the network 104. For example, theappliance 200 may be designed, constructed or adapted to perform WANoptimization techniques discussed herein without a second cooperatingappliance 200′. In other embodiments as depicted on the bottom of FIG.1C, a single appliance 200 may be deployed with one or more secondappliances 205. For example, a WAN acceleration first appliance 200,such as a Citrix WANScaler appliance, may be deployed with a LANaccelerating or Application Firewall second appliance 205, such as aCitrix NetScaler appliance.

Computing Device

The client 102, server 106, and appliance 200 and 205 may be deployed asand/or executed on any type and form of computing device, such as acomputer, network device or appliance capable of communicating on anytype and form of network and performing the operations described herein.FIGS. 1D and 1E depict block diagrams of a computing device 100 usefulfor practicing an embodiment of the client 102, server 106 or appliance200. As shown in FIGS. 1D and 1E, each computing device 100 includes acentral processing unit 101, and a main memory unit 122. As shown inFIG. 1D, a computing device 100 may include a visual display device 124,a keyboard 126 and/or a pointing device 127, such as a mouse. Eachcomputing device 100 may also include additional optional elements, suchas one or more input/output devices 130 a-130 b (generally referred tousing reference numeral 130), and a cache memory 140 in communicationwith the central processing unit 101.

The central processing unit 101 is any logic circuitry that responds toand processes instructions fetched from the main memory unit 122. Inmany embodiments, the central processing unit is provided by amicroprocessor unit, such as: those manufactured by Intel Corporation ofMountain View, Calif.; those manufactured by Motorola Corporation ofSchaumburg, Ill.; those manufactured by Transmeta Corporation of SantaClara, Calif.; the RS/6000 processor, those manufactured byInternational Business Machines of White Plains, N.Y.; or thosemanufactured by Advanced Micro Devices of Sunnyvale, Calif. Thecomputing device 100 may be based on any of these processors, or anyother processor capable of operating as described herein.

Main memory unit 122 may be one or more memory chips capable of storingdata and allowing any storage location to be directly accessed by themicroprocessor 101, such as Static random access memory (SRAM), BurstSRAM or SynchBurst SRAM (BSRAM), Dynamic random access memory (DRAM),Fast Page Mode DRAM (FPM DRAM), Enhanced DRAM (EDRAM), Extended DataOutput RAM (EDO RAM), Extended Data Output DRAM (EDO DRAM), BurstExtended Data Output DRAM (BEDO DRAM), Enhanced DRAM (EDRAM),synchronous DRAM (SDRAM), JEDEC SRAM, PC100 SDRAM, Double Data RateSDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), SyncLink DRAM (SLDRAM),Direct Rambus DRAM (DRDRAM), or Ferroelectric RAM (FRAM). The mainmemory 122 may be based on any of the above described memory chips, orany other available memory chips capable of operating as describedherein. In the embodiment shown in FIG. 1D, the processor 101communicates with main memory 122 via a system bus 150 (described inmore detail below). FIG. 1D depicts an embodiment of a computing device100 in which the processor communicates directly with main memory 122via a memory port 103. For example, in FIG. 1E the main memory 122 maybe DRDRAM.

FIG. 1E depicts an embodiment in which the main processor 101communicates directly with cache memory 140 via a secondary bus,sometimes referred to as a backside bus. In other embodiments, the mainprocessor 101 communicates with cache memory 140 using the system bus150. Cache memory 140 typically has a faster response time than mainmemory 122 and is typically provided by SRAM, BSRAM, or EDRAM. In theembodiment shown in FIG. 1D, the processor 101 communicates with variousI/O devices 130 via a local system bus 150. Various busses may be usedto connect the central processing unit 101 to any of the I/O devices130, including a VESA VL bus, an ISA bus, an EISA bus, a MicroChannelArchitecture (MCA) bus, a PCI bus, a PCI-X bus, a PCI-Express bus, or aNuBus. For embodiments in which the I/O device is a video display 124,the processor 101 may use an Advanced Graphics Port (AGP) to communicatewith the display 124. FIG. 1E depicts an embodiment of a computer 100 inwhich the main processor 101 communicates directly with I/O device 130via HyperTransport, Rapid I/O, or InfiniBand. FIG. 1E also depicts anembodiment in which local busses and direct communication are mixed: theprocessor 101 communicates with I/O device 130 using a localinterconnect bus while communicating with I/O device 130 directly.

The computing device 100 may support any suitable installation device116, such as a floppy disk drive for receiving floppy disks such as3.5-inch, 5.25-inch disks or ZIP disks, a CD-ROM drive, a CD-R/RW drive,a DVD-ROM drive, tape drives of various formats, USB device, hard-driveor any other device suitable for installing software and programs suchas any client agent 120, or portion thereof. The computing device 100may further comprise a storage device 128, such as one or more hard diskdrives or redundant arrays of independent disks, for storing anoperating system and other related software, and for storing applicationsoftware programs such as any program related to the client agent 120.Optionally, any of the installation devices 116 could also be used asthe storage device 128. Additionally, the operating system and thesoftware can be run from a bootable medium, for example, a bootable CD,such as KNOPPIX®, a bootable CD for GNU/Linux that is available as aGNU/Linux distribution from knoppix.net.

Furthermore, the computing device 100 may include a network interface118 to interface to a Local Area Network (LAN), Wide Area Network (WAN)or the Internet through a variety of connections including, but notlimited to, standard telephone lines, LAN or WAN links (e.g., 802.11,T1, T3, 56 kb, X.25), broadband connections (e.g., ISDN, Frame Relay,ATM), wireless connections, or some combination of any or all of theabove. The network interface 118 may comprise a built-in networkadapter, network interface card, PCMCIA network card, card bus networkadapter, wireless network adapter, USB network adapter, modem or anyother device suitable for interfacing the computing device 100 to anytype of network capable of communication and performing the operationsdescribed herein.

A wide variety of I/O devices 130 a-130 n may be present in thecomputing device 100. Input devices include keyboards, mice, trackpads,trackballs, microphones, and drawing tablets. Output devices includevideo displays, speakers, inkjet printers, laser printers, anddye-sublimation printers. The I/O devices 130 may be controlled by anI/O controller 123 as shown in FIG. 1D. The I/O controller may controlone or more I/O devices such as a keyboard 126 and a pointing device127, e.g., a mouse or optical pen. Furthermore, an I/O device may alsoprovide storage 128 and/or an installation medium 116 for the computingdevice 100. In still other embodiments, the computing device 100 mayprovide USB connections to receive handheld USB storage devices such asthe USB Flash Drive line of devices manufactured by Twintech Industry,Inc. of Los Alamitos, Calif.

In some embodiments, the computing device 100 may comprise or beconnected to multiple display devices 124 a-124 n, which each may be ofthe same or different type and/or form. As such, any of the I/O devices130 a-130 n and/or the I/O controller 123 may comprise any type and/orform of suitable hardware, software, or combination of hardware andsoftware to support, enable or provide for the connection and use ofmultiple display devices 124 a-124 n by the computing device 100. Forexample, the computing device 100 may include any type and/or form ofvideo adapter, video card, driver, and/or library to interface,communicate, connect or otherwise use the display devices 124 a-124 n.In one embodiment, a video adapter may comprise multiple connectors tointerface to multiple display devices 124 a-124 n. In other embodiments,the computing device 100 may include multiple video adapters, with eachvideo adapter connected to one or more of the display devices 124 a-124n. In some embodiments, any portion of the operating system of thecomputing device 100 may be configured for using multiple displays 124a-124 n. In other embodiments, one or more of the display devices 124a-124 n may be provided by one or more other computing devices, such ascomputing devices 100 a and 100 b connected to the computing device 100,for example, via a network. These embodiments may include any type ofsoftware designed and constructed to use another computer's displaydevice as a second display device 124 a for the computing device 100.One ordinarily skilled in the art will recognize and appreciate thevarious ways and embodiments that a computing device 100 may beconfigured to have multiple display devices 124 a-124 n.

In further embodiments, a I/O device 130 may be a bridge 170 between thesystem bus 150 and an external communication bus, such as a USB bus, anApple Desktop Bus, an RS-232 serial connection, a SCSI bus, a FireWirebus, a FireWire 800 bus, an Ethernet bus, an AppleTalk bus, a GigabitEthernet bus, an Asynchronous Transfer Mode bus, a HIPPI bus, a SuperHIPPI bus, a SerialPlus bus, a SCI/LAMP bus, a FibreChannel bus, or aSerial Attached small computer system interface bus.

A computing device 100 of the sort depicted in FIGS. 1D and 1E typicallyoperate under the control of operating systems, which control schedulingof tasks and access to system resources. The computing device 100 can berunning any operating system such as any of the versions of theMicrosoft® Windows operating systems, the different releases of the Unixand Linux operating systems, any version of the Mac OS® for Macintoshcomputers, any embedded operating system, any real-time operatingsystem, any open source operating system, any proprietary operatingsystem, any operating systems for mobile computing devices, or any otheroperating system capable of running on the computing device andperforming the operations described herein. Typical operating systemsinclude: WINDOWS 3.x, WINDOWS 95, WINDOWS 98, WINDOWS 2000, WINDOWS NT3.51, WINDOWS NT 4.0, WINDOWS CE, and WINDOWS XP, all of which aremanufactured by Microsoft Corporation of Redmond, Wash.; MacOS,manufactured by Apple Computer of Cupertino, Calif.; OS/2, manufacturedby International Business Machines of Armonk, N.Y.; and Linux, afreely-available operating system distributed by Caldera Corp. of SaltLake City, Utah, or any type and/or form of a Unix operating system,among others.

In other embodiments, the computing device 100 may have differentprocessors, operating systems, and input devices consistent with thedevice. For example, in one embodiment the computer 100 is a Treo 180,270, 1060, 600 or 650 smart phone manufactured by Palm, Inc. In thisembodiment, the Treo smart phone is operated under the control of thePalmOS operating system and includes a stylus input device as well as afive-way navigator device. Moreover, the computing device 100 can be anyworkstation, desktop computer, laptop or notebook computer, server,handheld computer, mobile telephone, any other computer, or other formof computing or telecommunications device that is capable ofcommunication and that has sufficient processor power and memorycapacity to perform the operations described herein.

B. System and Appliance Architecture

Referring now to FIG. 2A, an embodiment of a system environment andarchitecture of an appliance 200 for delivering and/or operating acomputing environment on a client is depicted. In some embodiments, aserver 106 includes an application delivery system 290 for delivering acomputing environment or an application and/or data file to one or moreclients 102. In brief overview, a client 102 is in communication with aserver 106 via network 104 and appliance 200. For example, the client102 may reside in a remote office of a company, e.g., a branch office,and the server 106 may reside at a corporate data center. The client 102has a client agent 120, and a computing environment 215. The computingenvironment 215 may execute or operate an application that accesses,processes or uses a data file. The computing environment 215,application and/or data file may be delivered via the appliance 200and/or the server 106.

In some embodiments, the appliance 200 accelerates delivery of acomputing environment 215, or any portion thereof, to a client 102. Inone embodiment, the appliance 200 accelerates the delivery of thecomputing environment 215 by the application delivery system 290. Forexample, the embodiments described herein may be used to acceleratedelivery of a streaming application and data file able to be processedby the application from a central corporate data center to a remote userlocation, such as a branch office of the company. In another embodiment,the appliance 200 accelerates transport layer traffic between a client102 and a server 106. In another embodiment, the appliance 200 controls,manages, or adjusts the transport layer protocol to accelerate deliveryof the computing environment. In some embodiments, the appliance 200uses caching and/or compression techniques to accelerate delivery of acomputing environment.

In some embodiments, the application delivery management system 290provides application delivery techniques to deliver a computingenvironment to a desktop of a user, remote or otherwise, based on aplurality of execution methods and based on any authentication andauthorization policies applied via a policy engine 295. With thesetechniques, a remote user may obtain a computing environment and accessto server stored applications and data files from any network connecteddevice 100. In one embodiment, the application delivery system 290 mayreside or execute on a server 106. In another embodiment, theapplication delivery system 290 may reside or execute on a plurality ofservers 106 a-106 n. In some embodiments, the application deliverysystem 290 may execute in a server farm 38. In one embodiment, theserver 106 executing the application delivery system 290 may also storeor provide the application and data file. In another embodiment, a firstset of one or more servers 106 may execute the application deliverysystem 290, and a different server 106 n may store or provide theapplication and data file. In some embodiments, each of the applicationdelivery system 290, the application, and data file may reside or belocated on different servers. In yet another embodiment, any portion ofthe application delivery system 290 may reside, execute or be stored onor distributed to the appliance 200, or a plurality of appliances.

The client 102 may include a computing environment 215 for executing anapplication that uses or processes a data file. The client 102 vianetworks 104, 104′ and appliance 200 may request an application and datafile from the server 106. In one embodiment, the appliance 200 mayforward a request from the client 102 to the server 106. For example,the client 102 may not have the application and data file stored oraccessible locally. In response to the request, the application deliverysystem 290 and/or server 106 may deliver the application and data fileto the client 102. For example, in one embodiment, the server 106 maytransmit the application as an application stream to operate incomputing environment 215 on client 102.

In some embodiments, the application delivery system 290 comprises anyportion of the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™ and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application delivery system 290 may deliver one ormore applications to clients 102 or users via a remote-display protocolor otherwise via remote-based or server-based computing. In anotherembodiment, the application delivery system 290 may deliver one or moreapplications to clients or users via steaming of the application.

In one embodiment, the application delivery system 290 includes a policyengine 295 for controlling and managing the access to, selection ofapplication execution methods and the delivery of applications. In someembodiments, the policy engine 295 determines the one or moreapplications a user or client 102 may access. In another embodiment, thepolicy engine 295 determines how the application should be delivered tothe user or client 102, e.g., the method of execution. In someembodiments, the application delivery system 290 provides a plurality ofdelivery techniques from which to select a method of applicationexecution, such as a server-based computing, streaming or delivering theapplication locally to the client 120 for local execution.

In one embodiment, a client 102 requests execution of an applicationprogram and the application delivery system 290 comprising a server 106selects a method of executing the application program. In someembodiments, the server 106 receives credentials from the client 102. Inanother embodiment, the server 106 receives a request for an enumerationof available applications from the client 102. In one embodiment, inresponse to the request or receipt of credentials, the applicationdelivery system 290 enumerates a plurality of application programsavailable to the client 102. The application delivery system 290receives a request to execute an enumerated application. The applicationdelivery system 290 selects one of a predetermined number of methods forexecuting the enumerated application, for example, responsive to apolicy of a policy engine. The application delivery system 290 mayselect a method of execution of the application enabling the client 102to receive application-output data generated by execution of theapplication program on a server 106. The application delivery system 290may select a method of execution of the application enabling the clientor local machine 102 to execute the application program locally afterretrieving a plurality of application files comprising the application.In yet another embodiment, the application delivery system 290 mayselect a method of execution of the application to stream theapplication via the network 104 to the client 102.

A client 102 may execute, operate or otherwise provide an application,which can be any type and/or form of software, program, or executableinstructions such as any type and/or form of web browser, web-basedclient, client-server application, a thin-client computing client, anActiveX control, or a Java applet, or any other type and/or form ofexecutable instructions capable of executing on client 102. In someembodiments, the application may be a server-based or a remote-basedapplication executed on behalf of the client 102 on a server 106. In oneembodiment the server 106 may display output to the client 102 using anythin-client or remote-display protocol, such as the IndependentComputing Architecture (ICA) protocol manufactured by Citrix Systems,Inc. of Ft. Lauderdale, Fla. or the Remote Desktop Protocol (RDP)manufactured by the Microsoft Corporation of Redmond, Wash. Theapplication can use any type of protocol and it can be, for example, anHTTP client, an FTP client, an Oscar client, or a Telnet client. Inother embodiments, the application comprises any type of softwarerelated to VoIP communications, such as a soft IP telephone. In furtherembodiments, the application comprises any application related toreal-time data communications, such as applications for streaming videoand/or audio.

In some embodiments, the server 106 or a server farm 38 may be runningone or more applications, such as an application providing a thin-clientcomputing or remote display presentation application. In one embodiment,the server 106 or server farm 38 executes as an application, any portionof the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™, and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application is an ICA client, developed by CitrixSystems, Inc. of Fort Lauderdale, Fla. In other embodiments, theapplication includes a Remote Desktop (RDP) client, developed byMicrosoft Corporation of Redmond, Wash. Also, the server 106 may run anapplication, which for example, may be an application server providingemail services such as Microsoft Exchange manufactured by the MicrosoftCorporation of Redmond, Wash., a web or Internet server, or a desktopsharing server, or a collaboration server. In some embodiments, any ofthe applications may comprise any type of hosted service or products,such as GoToMeeting™ provided by Citrix Online Division, Inc. of SantaBarbara, Calif., WebEx™ provided by WebEx, Inc. of Santa Clara, Calif.,or Microsoft Office Live Meeting provided by Microsoft Corporation ofRedmond, Wash.

Example Appliance Architecture

FIG. 2A also illustrates an example embodiment of the appliance 200. Thearchitecture of the appliance 200 in FIG. 2A is provided by way ofillustration only and is not intended to be limiting in any manner. Theappliance 200 may include any type and form of computing device 100,such as any element or portion described in conjunction with FIGS. 1Dand 1E above. In brief overview, the appliance 200 has one or morenetwork ports 266A-226N and one or more networks stacks 267A-267N forreceiving and/or transmitting communications via networks 104. Theappliance 200 also has a network optimization engine 250 for optimizing,accelerating or otherwise improving the performance, operation, orquality of any network traffic or communications traversing theappliance 200.

The appliance 200 includes or is under the control of an operatingsystem. The operating system of the appliance 200 may be any type and/orform of Unix operating system although the disclosure is not so limited.As such, the appliance 200 can be running any operating system such asany of the versions of the Microsoft® Windows operating systems, thedifferent releases of the Unix and Linux operating systems, any versionof the Mac OS® for Macintosh computers, any embedded operating system,any network operating system, any real-time operating system, any opensource operating system, any proprietary operating system, any operatingsystems for mobile computing devices or network devices, or any otheroperating system capable of running on the appliance 200 and performingthe operations described herein.

The operating system of appliance 200 allocates, manages, or otherwisesegregates the available system memory into what is referred to askernel or system space, and user or application space. The kernel spaceis typically reserved for running the kernel, including any devicedrivers, kernel extensions or other kernel related software. As known tothose skilled in the art, the kernel is the core of the operatingsystem, and provides access, control, and management of resources andhardware-related elements of the appliance 200. In accordance with anembodiment of the appliance 200, the kernel space also includes a numberof network services or processes working in conjunction with the networkoptimization engine 250, or any portion thereof. Additionally, theembodiment of the kernel will depend on the embodiment of the operatingsystem installed, configured, or otherwise used by the device 200. Incontrast to kernel space, user space is the memory area or portion ofthe operating system used by user mode applications or programsotherwise running in user mode. A user mode application may not accesskernel space directly and uses service calls in order to access kernelservices. The operating system uses the user or application space forexecuting or running applications and provisioning of user levelprograms, services, processes and/or tasks.

The appliance 200 has one or more network ports 266 for transmitting andreceiving data over a network 104. The network port 266 provides aphysical and/or logical interface between the computing device and anetwork 104 or another device 100 for transmitting and receiving networkcommunications. The type and form of network port 266 depends on thetype and form of network and type of medium for connecting to thenetwork. Furthermore, any software of, provisioned for or used by thenetwork port 266 and network stack 267 may run in either kernel space oruser space.

In one embodiment, the appliance 200 has one network stack 267, such asa TCP/IP based stack, for communicating on a network 105, such with theclient 102 and/or the server 106. In one embodiment, the network stack267 is used to communicate with a first network, such as network 104,and also with a second network 104′. In another embodiment, theappliance 200 has two or more network stacks, such as first networkstack 267A and a second network stack 267N. The first network stack 267Amay be used in conjunction with a first port 266A to communicate on afirst network 104. The second network stack 267N may be used inconjunction with a second port 266N to communicate on a second network104′. In one embodiment, the network stack(s) 267 has one or morebuffers for queuing one or more network packets for transmission by theappliance 200.

The network stack 267 includes any type and form of software, orhardware, or any combinations thereof, for providing connectivity to andcommunications with a network. In one embodiment, the network stack 267includes a software implementation for a network protocol suite. Thenetwork stack 267 may have one or more network layers, such as anynetworks layers of the Open Systems Interconnection (OSI) communicationsmodel as those skilled in the art recognize and appreciate. As such, thenetwork stack 267 may have any type and form of protocols for any of thefollowing layers of the OSI model: 1) physical link layer, 2) data linklayer, 3) network layer, 4) transport layer, 5) session layer, 6)presentation layer, and 7) application layer. In one embodiment, thenetwork stack 267 includes a transport control protocol (TCP) over thenetwork layer protocol of the internet protocol (IP), generally referredto as TCP/IP. In some embodiments, the TCP/IP protocol may be carriedover the Ethernet protocol, which may comprise any of the family of IEEEwide-area-network (WAN) or local-area-network (LAN) protocols, such asthose protocols covered by the IEEE 802.3. In some embodiments, thenetwork stack 267 has any type and form of a wireless protocol, such asIEEE 802.11 and/or mobile internet protocol.

In view of a TCP/IP based network, any TCP/IP based protocol may beused, including Messaging Application Programming Interface (MAPI)(email), File Transfer Protocol (FTP), HyperText Transfer Protocol(HTTP), Common Internet File System (CIFS) protocol (file transfer),Independent Computing Architecture (ICA) protocol, Remote DesktopProtocol (RDP), Wireless Application Protocol (WAP), Mobile IP protocol,and Voice Over IP (VoIP) protocol. In another embodiment, the networkstack 267 comprises any type and form of transport control protocol,such as a modified transport control protocol, for example a TransactionTCP (T/TCP), TCP with selection acknowledgements (TCP-SACK), TCP withlarge windows (TCP-LW), a congestion prediction protocol such as theTCP-Vegas protocol, and a TCP spoofing protocol. In other embodiments,any type and form of user datagram protocol (UDP), such as UDP over IP,may be used by the network stack 267, such as for voice communicationsor real-time data communications.

Furthermore, the network stack 267 may include one or more networkdrivers supporting the one or more layers, such as a TCP driver or anetwork layer driver. The network drivers may be included as part of theoperating system of the computing device 100 or as part of any networkinterface cards or other network access components of the computingdevice 100. In some embodiments, any of the network drivers of thenetwork stack 267 may be customized, modified or adapted to provide acustom or modified portion of the network stack 267 in support of any ofthe techniques described herein.

In one embodiment, the appliance 200 provides for or maintains atransport layer connection between a client 102 and server 106 using asingle network stack 267. In some embodiments, the appliance 200effectively terminates the transport layer connection by changing,managing or controlling the behavior of the transport control protocolconnection between the client and the server. In these embodiments, theappliance 200 may use a single network stack 267. In other embodiments,the appliance 200 terminates a first transport layer connection, such asa TCP connection of a client 102, and establishes a second transportlayer connection to a server 106 for use by or on behalf of the client102, e.g., the second transport layer connection is terminated at theappliance 200 and the server 106. The first and second transport layerconnections may be established via a single network stack 267. In otherembodiments, the appliance 200 may use multiple network stacks, forexample 267A and 267N. In these embodiments, the first transport layerconnection may be established or terminated at one network stack 267A,and the second transport layer connection may be established orterminated on the second network stack 267N. For example, one networkstack may be for receiving and transmitting network packets on a firstnetwork, and another network stack for receiving and transmittingnetwork packets on a second network.

As shown in FIG. 2A, the network optimization engine 250 includes one ormore of the following elements, components or modules: network packetprocessing engine 240, LAN/WAN detector 210, flow controller 220, QoSengine 236, protocol accelerator 234, compression engine 238, cachemanager 232 and policy engine 295′. The network optimization engine 250,or any portion thereof, may include software, hardware or anycombination of software and hardware. Furthermore, any software of,provisioned for or used by the network optimization engine 250 may runin either kernel space or user space. For example, in one embodiment,the network optimization engine 250 may run in kernel space. In anotherembodiment, the network optimization engine 250 may run in user space.In yet another embodiment, a first portion of the network optimizationengine 250 runs in kernel space while a second portion of the networkoptimization engine 250 runs in user space.

Network Packet Processing Engine

The network packet engine 240, also generally referred to as a packetprocessing engine or packet engine, is responsible for controlling andmanaging the processing of packets received and transmitted by appliance200 via network ports 266 and network stack(s) 267. The network packetengine 240 may operate at any layer of the network stack 267. In oneembodiment, the network packet engine 240 operates at layer 2 or layer 3of the network stack 267. In some embodiments, the packet engine 240intercepts or otherwise receives packets at the network layer, such asthe IP layer in a TCP/IP embodiment. In another embodiment, the packetengine 240 operates at layer 4 of the network stack 267. For example, insome embodiments, the packet engine 240 intercepts or otherwise receivespackets at the transport layer, such as intercepting packets as the TCPlayer in a TCP/IP embodiment. In other embodiments, the packet engine240 operates at any session or application layer above layer 4. Forexample, in one embodiment, the packet engine 240 intercepts orotherwise receives network packets above the transport layer protocollayer, such as the payload of a TCP packet in a TCP embodiment.

The packet engine 240 may include a buffer for queuing one or morenetwork packets during processing, such as for receipt of a networkpacket or transmission of a network packet. Additionally, the packetengine 240 is in communication with one or more network stacks 267 tosend and receive network packets via network ports 266. The packetengine 240 may include a packet processing timer. In one embodiment, thepacket processing timer provides one or more time intervals to triggerthe processing of incoming, i.e., received, or outgoing, i.e.,transmitted, network packets. In some embodiments, the packet engine 240processes network packets responsive to the timer. The packet processingtimer provides any type and form of signal to the packet engine 240 tonotify, trigger, or communicate a time related event, interval oroccurrence. In many embodiments, the packet processing timer operates inthe order of milliseconds, such as for example 100 ms, 50 ms, 25 ms, 10ms, 5 ms or 1 ms.

During operations, the packet engine 240 may be interfaced, integratedor be in communication with any portion of the network optimizationengine 250, such as the LAN/WAN detector 210, flow controller 220, QoSengine 236, protocol accelerator 234, compression engine 238, cachemanager 232 and/or policy engine 295′. As such, any of the logic,functions, or operations of the LAN/WAN detector 210, flow controller220, QoS engine 236, protocol accelerator 234, compression engine 238,cache manager 232 and policy engine 295′ may be performed responsive tothe packet processing timer and/or the packet engine 240. In someembodiments, any of the logic, functions, or operations of theencryption engine 234, cache manager 232, policy engine 236 andmulti-protocol compression logic 238 may be performed at the granularityof time intervals provided via the packet processing timer, for example,at a time interval of less than or equal to 10 ms. For example, in oneembodiment, the cache manager 232 may perform expiration of any cachedobjects responsive to the integrated packet engine 240 and/or the packetprocessing timer 242. In another embodiment, the expiry or invalidationtime of a cached object can be set to the same order of granularity asthe time interval of the packet processing timer, such as at every 10ms.

Cache Manager

The cache manager 232 may include software, hardware or any combinationof software and hardware to store data, information and objects to acache in memory or storage, provide cache access, and control and managethe cache. The data, objects or content processed and stored by thecache manager 232 may include data in any format, such as a markuplanguage, or any type of data communicated via any protocol. In someembodiments, the cache manager 232 duplicates original data storedelsewhere or data previously computed, generated or transmitted, inwhich the original data may require longer access time to fetch, computeor otherwise obtain relative to reading a cache memory or storageelement. Once the data is stored in the cache, future use can be made byaccessing the cached copy rather than refetching or recomputing theoriginal data, thereby reducing the access time. In some embodiments,the cache may comprise a data object in memory of the appliance 200. Inanother embodiment, the cache may comprise any type and form of storageelement of the appliance 200, such as a portion of a hard disk. In someembodiments, the processing unit of the device may provide cache memoryfor use by the cache manager 232. In yet further embodiments, the cachemanager 232 may use any portion and combination of memory, storage, orthe processing unit for caching data, objects, and other content.

Furthermore, the cache manager 232 includes any logic, functions, rules,or operations to perform any caching techniques of the appliance 200. Insome embodiments, the cache manager 232 may operate as an application,library, program, service, process, thread or task. In some embodiments,the cache manager 232 can comprise any type of general purpose processor(GPP), or any other type of integrated circuit, such as a FieldProgrammable Gate Array (FPGA), Programmable Logic Device (PLD), orApplication Specific Integrated Circuit (ASIC).

Policy Engine

The policy engine 295′ includes any logic, function or operations forproviding and applying one or more policies or rules to the function,operation or configuration of any portion of the appliance 200. Thepolicy engine 295′ may include, for example, an intelligent statisticalengine or other programmable application(s). In one embodiment, thepolicy engine 295 provides a configuration mechanism to allow a user toidentify, specify, define or configure a policy for the networkoptimization engine 250, or any portion thereof. For example, the policyengine 295 may provide policies for what data to cache, when to cachethe data, for whom to cache the data, when to expire an object in cacheor refresh the cache. In other embodiments, the policy engine 236 mayinclude any logic, rules, functions or operations to determine andprovide access, control and management of objects, data or content beingcached by the appliance 200 in addition to access, control andmanagement of security, network traffic, network access, compression orany other function or operation performed by the appliance 200.

In some embodiments, the policy engine 295′ provides and applies one ormore policies based on any one or more of the following: a user,identification of the client, identification of the server, the type ofconnection, the time of the connection, the type of network, or thecontents of the network traffic. In one embodiment, the policy engine295′ provides and applies a policy based on any field or header at anyprotocol layer of a network packet. In another embodiment, the policyengine 295′ provides and applies a policy based on any payload of anetwork packet. For example, in one embodiment, the policy engine 295′applies a policy based on identifying a certain portion of content of anapplication layer protocol carried as a payload of a transport layerpacket. In another example, the policy engine 295′ applies a policybased on any information identified by a client, server or usercertificate. In yet another embodiment, the policy engine 295′ applies apolicy based on any attributes or characteristics obtained about aclient 102, such as via any type and form of endpoint detection (see forexample the collection agent of the client agent discussed below).

In one embodiment, the policy engine 295′ works in conjunction orcooperation with the policy engine 295 of the application deliverysystem 290. In some embodiments, the policy engine 295′ is a distributedportion of the policy engine 295 of the application delivery system 290.In another embodiment, the policy engine 295 of the application deliverysystem 290 is deployed on or executed on the appliance 200. In someembodiments, the policy engines 295, 295′ both operate on the appliance200. In yet another embodiment, the policy engine 295′, or a portionthereof, of the appliance 200 operates on a server 106.

Multi-Protocol and Multi-Layer Compression Engine

The compression engine 238 includes any logic, business rules, functionor operations for compressing one or more protocols of a network packet,such as any of the protocols used by the network stack 267 of theappliance 200. The compression engine 238 may also be referred to as amulti-protocol compression engine 238 in that it may be designed,constructed or capable of compressing a plurality of protocols. In oneembodiment, the compression engine 238 applies context insensitivecompression, which is compression applied to data without knowledge ofthe type of data. In another embodiment, the compression engine 238applies context-sensitive compression. In this embodiment, thecompression engine 238 utilizes knowledge of the data type to select aspecific compression algorithm from a suite of suitable algorithms. Insome embodiments, knowledge of the specific protocol is used to performcontext-sensitive compression. In one embodiment, the appliance 200 orcompression engine 238 can use port numbers (e.g., well-known ports), aswell as data from the connection itself to determine the appropriatecompression algorithm to use. Some protocols use only a single type ofdata, requiring only a single compression algorithm that can be selectedwhen the connection is established. Other protocols contain differenttypes of data at different times. For example, POP, IMAP, SMTP, and HTTPall move files of arbitrary types interspersed with other protocol data.

In one embodiment, the compression engine 238 uses a delta-typecompression algorithm. In another embodiment, the compression engine 238uses first site compression as well as searching for repeated patternsamong data stored in cache, memory or disk. In some embodiments, thecompression engine 238 uses a lossless compression algorithm. In otherembodiments, the compression engine uses a lossy compression algorithm.In some cases, knowledge of the data type and, sometimes, permissionfrom the user are required to use a lossy compression algorithm.Compression is not limited to the protocol payload. The control fieldsof the protocol itself may be compressed. In some embodiments, thecompression engine 238 uses a different algorithm than that used for thepayload.

In some embodiments, the compression engine 238 compresses at one ormore layers of the network stack 267. In one embodiment, the compressionengine 238 compresses at a transport layer protocol. In anotherembodiment, the compression engine 238 compresses at an applicationlayer protocol. In some embodiments, the compression engine 238compresses at a layer 2-4 protocol. In other embodiments, thecompression engine 238 compresses at a layer 5-7 protocol. In yetanother embodiment, the compression engine compresses a transport layerprotocol and an application layer protocol. In some embodiments, thecompression engine 238 compresses a layer 2-4 protocol and a layer 5-7protocol.

In some embodiments, the compression engine 238 uses memory-basedcompression, cache-based compression or disk-based compression or anycombination thereof. As such, the compression engine 238 may be referredto as a multi-layer compression engine. In one embodiment, thecompression engine 238 uses a history of data stored in memory, such asRAM. In another embodiment, the compression engine 238 uses a history ofdata stored in a cache, such as L2 cache of the processor. In otherembodiments, the compression engine 238 uses a history of data stored toa disk or storage location. In some embodiments, the compression engine238 uses a hierarchy of cache-based, memory-based and disk-based datahistory. The compression engine 238 may first use the cache-based datato determine one or more data matches for compression, and then maycheck the memory-based data to determine one or more data matches forcompression. In another case, the compression engine 238 may check diskstorage for data matches for compression after checking either thecache-based and/or memory-based data history.

In one embodiment, multi-protocol compression engine 238 compressesbi-directionally between clients 102 a-102 n and servers 106 a-106 n anyTCP/IP based protocol, including Messaging Application ProgrammingInterface (MAPI) (email), File Transfer Protocol (FTP), HyperTextTransfer Protocol (HTTP), Common Internet File System (CIFS) protocol(file transfer), Independent Computing Architecture (ICA) protocol,Remote Desktop Protocol (RDP), Wireless Application Protocol (WAP),Mobile IP protocol, and Voice Over IP (VoIP) protocol. In otherembodiments, multi-protocol compression engine 238 provides compressionof HyperText Markup Language (HTML) based protocols and in someembodiments, provides compression of any markup languages, such as theExtensible Markup Language (XML). In one embodiment, the multi-protocolcompression engine 238 provides compression of any high-performanceprotocol, such as any protocol designed for appliance 200 to appliance200 communications. In another embodiment, the multi-protocolcompression engine 238 compresses any payload of or any communicationusing a modified transport control protocol, such as Transaction TCP(T/TCP), TCP with selection acknowledgements (TCP-SACK), TCP with largewindows (TCP-LW), a congestion prediction protocol such as the TCP-Vegasprotocol, and a TCP spoofing protocol.

As such, the multi-protocol compression engine 238 acceleratesperformance for users accessing applications via desktop clients, e.g.,Microsoft Outlook and non-Web thin clients, such as any client launchedby popular enterprise applications like Oracle, SAP and Siebel, and evenmobile clients, such as the Pocket PC. In some embodiments, themulti-protocol compression engine by integrating with packet processingengine 240 accessing the network stack 267 is able to compress any ofthe protocols carried by a transport layer protocol, such as anyapplication layer protocol.

LAN/WAN Detector

The LAN/WAN detector 238 includes any logic, business rules, function oroperations for automatically detecting a slow side connection (e.g., awide area network (WAN) connection such as an Intranet) and associatedport 267, and a fast side connection (e.g., a local area network (LAN)connection) and an associated port 267. In some embodiments, the LAN/WANdetector 238 monitors network traffic on the network ports 267 of theappliance 200 to detect a synchronization packet, sometimes referred toas a “tagged” network packet. The synchronization packet identifies atype or speed of the network traffic. In one embodiment, thesynchronization packet identifies a WAN speed or WAN type connection.The LAN/WAN detector 238 also identifies receipt of an acknowledgementpacket to a tagged synchronization packet and on which port it isreceived. The appliance 200 then configures itself to operate theidentified port on which the tagged synchronization packet arrived sothat the speed on that port is set to be the speed associated with thenetwork connected to that port. The other port is then set to the speedassociated with the network connected to that port.

For ease of discussion herein, reference to “fast” side will be madewith respect to connection with a wide area network (WAN), e.g., theInternet, and operating at a network speed of the WAN. Likewise,reference to “slow” side will be made with respect to connection with alocal area network (LAN) and operating at a network speed the LAN.However, it is noted that “fast” and “slow” sides in a network canchange on a per-connection basis and are relative terms to the speed ofthe network connections or to the type of network topology. Suchconfigurations are useful in complex network topologies, where a networkis “fast” or “slow” only when compared to adjacent networks and not inany absolute sense.

In one embodiment, the LAN/WAN detector 238 may be used to allow forauto-discovery by an appliance 200 of a network to which it connects. Inanother embodiment, the LAN/WAN detector 238 may be used to detect theexistence or presence of a second appliance 200′ deployed in the network104. For example, an auto-discovery mechanism in operation in accordancewith FIG. 1A functions as follows: appliance 200 and 200′ are placed inline with the connection linking client 102 and server 106. Theappliances 200 and 200′ are at the ends of a low-speed link, e.g.,Internet, connecting two LANs. In one example embodiment, appliances 200and 200′ each include two ports—one to connect with the “lower” speedlink and the other to connect with a “higher” speed link, e.g., a LAN.Any packet arriving at one port is copied to the other port. Thus,appliance 200 and 200′ are each configured to function as a bridgebetween the two networks 104.

When an end node, such as the client 102, opens a new TCP connectionwith another end node, such as the server 106, the client 102 sends aTCP packet with a synchronization (SYN) header bit set, or a SYN packet,to the server 106. In the present example, client 102 opens a transportlayer connection to server 106. When the SYN packet passes throughappliance 200, the appliance 200 inserts, attaches or otherwise providesa characteristic TCP header option to the packet, which announces itspresence. If the packet passes through a second appliance, in thisexample appliance 200′ the second appliance notes the header option onthe SYN packet. The server 106 responds to the SYN packet with asynchronization acknowledgment (SYN-ACK) packet. When the SYN-ACK packetpasses through appliance 200′, a TCP header option is tagged (e.g.,attached, inserted or added) to the SYN-ACK packet to announce appliance200′ presence to appliance 200. When appliance 200 receives this packet,both appliances 200, 200′ are now aware of each other and the connectioncan be appropriately accelerated.

Further to the operations of the LAN/WAN detector 238, a method orprocess for detecting “fast” and “slow” sides of a network using a SYNpacket is described. During a transport layer connection establishmentbetween a client 102 and a server 106, the appliance 200 via the LAN/WANdetector 238 determines whether the SYN packet is tagged with anacknowledgement (ACK). If it is tagged, the appliance 200 identifies orconfigures the port receiving the tagged SYN packet (SYN-ACK) as the“slow” side. In one embodiment, the appliance 200 optionally removes theACK tag from the packet before copying the packet to the other port. Ifthe LAN/WAN detector 238 determines that the packet is not tagged, theappliance 200 identifies or configure the port receiving the untaggedpacket as the “fast” side. The appliance 200 then tags the SYN packetwith an ACK and copies the packet to the other port.

In another embodiment, the LAN/WAN detector 238 detects fast and slowsides of a network using a SYN-ACK packet. The appliance 200 via theLAN/WAN detector 238 determines whether the SYN-ACK packet is taggedwith an acknowledgement (ACK). If it is tagged, the appliance 200identifies or configures the port receiving the tagged SYN packet(SYN-ACK) as the “slow” side. In one embodiment, the appliance 200optionally removes the ACK tag from the packet before copying the packetto the other port. If the LAN/WAN detector 238 determines that thepacket is not tagged, the appliance 200 identifies or configures theport receiving the untagged packet as the “fast” side. The LAN/WANdetector 238 determines whether the SYN packet was tagged. If the SYNpacket was not tagged, the appliance 200 copied the packet to the otherport. If the SYN packet was tagged, the appliance tags the SYN-ACKpacket before copying it to the other port.

The appliance 200, 200′ may add, insert, modify, attach or otherwiseprovide any information or data in the TCP option header to provide anyinformation, data or characteristics about the network connection,network traffic flow, or the configuration or operation of the appliance200. In this manner, not only does an appliance 200 announce itspresence to another appliance 200′ or tag a higher or lower speedconnection, the appliance 200 provides additional information and datavia the TCP option headers about the appliance or the connection. TheTCP option header information may be useful to or used by an appliancein controlling, managing, optimizing, acceleration or improving thenetwork traffic flow traversing the appliance 200, or to otherwiseconfigure itself or operation of a network port.

Although generally described in conjunction with detecting speeds ofnetwork connections or the presence of appliances, the LAN/WAN detector238 can be used for applying any type of function, logic or operation ofthe appliance 200 to a port, connection or flow of network traffic. Inparticular, automated assignment of ports can occur whenever a deviceperforms different functions on different ports, where the assignment ofa port to a task can be made during the unit's operation, and/or thenature of the network segment on each port is discoverable by theappliance 200.

Flow Control

The flow controller 220 includes any logic, business rules, function oroperations for optimizing, accelerating or otherwise improving theperformance, operation or quality of service of transport layercommunications of network packets or the delivery of packets at thetransport layer. A flow controller, also sometimes referred to as a flowcontrol module, regulates, manages and controls data transfer rates. Insome embodiments, the flow controller 220 is deployed at or connected ata bandwidth bottleneck in the network 104. In one embodiment, the flowcontroller 220 effectively regulates, manages and controls bandwidthusage or utilization. In other embodiments, the flow control modules mayalso be deployed at points on the network of latency transitions (lowlatency to high latency) and on links with media losses (such aswireless or satellite links).

In some embodiments, a flow controller 220 may include a receiver-sideflow control module for controlling the rate of receipt of networktransmissions and a sender-side flow control module for the controllingthe rate of transmissions of network packets. In other embodiments, afirst flow controller 220 includes a receiver-side flow control moduleand a second flow controller 220′ includes a sender-side flow controlmodule. In some embodiments, a first flow controller 220 is deployed ona first appliance 200 and a second flow controller 220′ is deployed on asecond appliance 200′. As such, in some embodiments, a first appliance200 controls the flow of data on the receiver side and a secondappliance 200′ controls the data flow from the sender side. In yetanother embodiment, a single appliance 200 includes flow control forboth the receiver-side and sender-side of network communicationstraversing the appliance 200.

In one embodiment, a flow control module 220 is configured to allowbandwidth at the bottleneck to be more fully utilized, and in someembodiments, not overutilized. In some embodiments, the flow controlmodule 220 transparently buffers (or rebuffers data already buffered by,for example, the sender) network sessions that pass between nodes havingassociated flow control modules 220. When a session passes through twoor more flow control modules 220, one or more of the flow controlmodules controls a rate of the session(s).

In one embodiment, the flow control module 200 is configured withpredetermined data relating to bottleneck bandwidth. In anotherembodiment, the flow control module 220 may be configured to detect thebottleneck bandwidth or data associated therewith. Unlike conventionalnetwork protocols such as TCP, a receiver-side flow control module 220controls the data transmission rate. The receiver-side flow controlmodule controls 220 the sender-side flow control module, e.g., 220, datatransmission rate by forwarding transmission rate limits to thesender-side flow control module 220. In one embodiment, thereceiver-side flow control module 220 piggybacks these transmission ratelimits on acknowledgement (ACK) packets (or signals) sent to the sender,e.g., client 102, by the receiver, e.g., server 106. The receiver-sideflow control module 220 does this in response to rate control requeststhat are sent by the sender side flow control module 220′. The requestsfrom the sender-side flow control module 220′ may be “piggybacked” ondata packets sent by the sender 106.

In some embodiments, the flow controller 220 manipulates, adjusts,simulates, changes, improves or otherwise adapts the behavior of thetransport layer protocol to provide improved performance or operationsof delivery, data rates and/or bandwidth utilization of the transportlayer. The flow controller 220 may implement a plurality of data flowcontrol techniques at the transport layer, including but not limitedto 1) pre-acknowledgements, 2) window virtualization, 3) recongestiontechniques, 3) local retransmission techniques, 4) wavefront detectionand disambiguation, 5) transport control protocol selectiveacknowledgements, 6) transaction boundary detection techniques and 7)repacketization.

Although a sender may be generally described herein as a client 102 anda receiver as a server 106, a sender may be any end point such as aserver 106 or any computing device 100 on the network 104. Likewise, areceiver may be a client 102 or any other computing device on thenetwork 104.

Pre-Acknowledgements

In brief overview of a pre-acknowledgement flow control technique, theflow controller 220, in some embodiments, handles the acknowledgementsand retransmits for a sender, effectively terminating the sender'sconnection with the downstream portion of a network connection. Inreference to FIG. 1B, one possible deployment of an appliance 200 into anetwork architecture to implement this feature is depicted. In thisexample environment, a sending computer or client 102 transmits data onnetwork 104, for example, via a switch, which determines that the datais destined for VPN appliance 205. Because of the chosen networktopology, all data destined for VPN appliance 205 traverses appliance200, so the appliance 200 can apply any necessary algorithms to thisdata.

Continuing further with the example, the client 102 transmits a packet,which is received by the appliance 200. When the appliance 200 receivesthe packet, which is transmitted from the client 102 to a recipient viathe VPN appliance 205 the appliance 200 retains a copy of the packet andforwards the packet downstream to the VPN appliance 205. The appliance200 then generates an acknowledgement packet (ACK) and sends the ACKpacket back to the client 102 or sending endpoint. This ACK, apre-acknowledgment, causes the sender 102 to believe that the packet hasbeen delivered successfully, freeing the sender's resources forsubsequent processing. The appliance 200 retains the copy of the packetdata in the event that a retransmission of the packet is required, sothat the sender 102 does not have to handle retransmissions of the data.This early generation of acknowledgements may be called “preacking.”

If a retransmission of the packet is required, the appliance 200retransmits the packet to the sender. The appliance 200 may determinewhether retransmission is required as a sender would in a traditionalsystem, for example, determining that a packet is lost if anacknowledgement has not been received for the packet after apredetermined amount of time. To this end, the appliance 200 monitorsacknowledgements generated by the receiving endpoint, e.g., server 106(or any other downstream network entity) so that it can determinewhether the packet has been successfully delivered or needs to beretransmitted. If the appliance 200 determines that the packet has beensuccessfully delivered, the appliance 200 is free to discard the savedpacket data. The appliance 200 may also inhibit forwardingacknowledgements for packets that have already been received by thesending endpoint.

In the embodiment described above, the appliance 200 via the flowcontroller 220 controls the sender 102 through the delivery ofpre-acknowledgements, also referred to as “preacks”, as though theappliance 200 was a receiving endpoint itself. Since the appliance 200is not an endpoint and does not actually consume the data, the appliance200 includes a mechanism for providing overflow control to the sendingendpoint. Without overflow control, the appliance 200 could run out ofmemory because the appliance 200 stores packets that have been preackedto the sending endpoint but not yet acknowledged as received by thereceiving endpoint. Therefore, in a situation in which the sender 102transmits packets to the appliance 200 faster than the appliance 200 canforward the packets downstream, the memory available in the appliance200 to store unacknowledged packet data can quickly fill. A mechanismfor overflow control allows the appliance 200 to control transmission ofthe packets from the sender 102 to avoid this problem.

In one embodiment, the appliance 200 or flow controller 220 includes aninherent “self-clocking” overflow control mechanism. This self-clockingis due to the order in which the appliance 200 may be designed totransmit packets downstream and send ACKs to the sender 102 or 106. Insome embodiments, the appliance 200 does not preack the packet untilafter it transmits the packet downstream. In this way, the sender 102will receive the ACKs at the rate at which the appliance 200 is able totransmit packets rather than the rate at which the appliance 200receives packets from the sender 100. This helps to regulate thetransmission of packets from a sender 102.

Window Virtualization

Another overflow control mechanism that the appliance 200 may implementis to use the TCP window size parameter, which tells a sender how muchbuffer the receiver is permitting the sender to fill up. A nonzerowindow size (e.g., a size of at least one Maximum Segment Size (MSS)) ina preack permits the sending endpoint to continue to deliver data to theappliance, whereas a zero window size inhibits further datatransmission. Accordingly, the appliance 200 may regulate the flow ofpackets from the sender, for example when the appliance's 200 buffer isbecoming full, by appropriately setting the TCP window size in eachpreack.

Another technique to reduce this additional overhead is to applyhysteresis. When the appliance 200 delivers data to the slower side, theoverflow control mechanism in the appliance 200 can require that aminimum amount of space be available before sending a nonzero windowadvertisement to the sender. In one embodiment, the appliance 200 waitsuntil there is a minimum of a predetermined number of packets, such asfour packets, of space available before sending a nonzero window packet,such as a window size of four packet). This reduces the overhead byapproximately a factor four, since only two ACK packets are sent foreach group of four data packets, instead of eight ACK packets for fourdata packets.

Another technique the appliance 200 or flow controller 220 may use foroverflow control is the TCP delayed ACK mechanism, which skips ACKs toreduce network traffic. The TCP delayed ACKs automatically delay thesending of an ACK, either until two packets are received or until afixed timeout has occurred. This mechanism alone can result in cuttingthe overhead in half; moreover, by increasing the numbers of packetsabove two, additional overhead reduction is realized. But merelydelaying the ACK itself may be insufficient to control overflow, and theappliance 200 may also use the advertised window mechanism on the ACKsto control the sender. When doing this, the appliance 200 in oneembodiment avoids triggering the timeout mechanism of the sender bydelaying the ACK too long.

In one embodiment, the flow controller 220 does not preack the lastpacket of a group of packets. By not preacking the last packet, or atleast one of the packets in the group, the appliance avoids a falseacknowledgement for a group of packets. For example, if the appliancewere to send a preack for a last packet and the packet were subsequentlylost, the sender would have been tricked into thinking that the packetis delivered when it was not. Thinking that the packet had beendelivered, the sender could discard that data. If the appliance alsolost the packet, there would be no way to retransmit the packet to therecipient. By not preacking the last packet of a group of packets, thesender will not discard the packet until it has been delivered.

In another embodiment, the flow controller 220 may use a windowvirtualization technique to control the rate of flow or bandwidthutilization of a network connection. Though it may not immediately beapparent from examining conventional literature such as RFC 1323, thereis effectively a send window for transport layer protocols such as TCP.The send window is similar to the receive window, in that it consumesbuffer space (though on the sender). The sender's send window consistsof all data sent by the application that has not been acknowledged bythe receiver. This data can be retained in memory in case retransmissionis required. Since memory is a shared resource, some TCP stackimplementations limit the size of this data. When the send window isfull, an attempt by an application program to send more data results inblocking the application program until space is available. Subsequentreception of acknowledgements will free send-window memory and unblockthe application program. In some embodiments, this window size is knownas the socket buffer size in some TCP implementations.

In one embodiment, the flow control module 220 is configured to provideaccess to increased window (or buffer) sizes. This configuration mayalso be referenced to as window virtualization. In the embodiment of TCPas the transport layer protocol, the TCP header includes a bit stringcorresponding to a window scale. In one embodiment, “window” may bereferenced in a context of send, receive, or both.

One embodiment of window virtualization is to insert a preackingappliance 200 into a TCP session. In reference to any of theenvironments of FIG. 1A or 1B, initiation of a data communicationsession between a source node, e.g., client 102 (for ease of discussion,now referenced as source node 102), and a destination node, e.g., server106 (for ease of discussion, now referenced as destination node 106) isestablished. For TCP communications, the source node 102 initiallytransmits a synchronization signal (“SYN”) through its local areanetwork 104 to first flow control module 220. The first flow controlmodule 220 inserts a configuration identifier into the TCP headeroptions area. The configuration identifier identifies this point in thedata path as a flow control module.

The appliances 200 via a flow control module 220 provide window (orbuffer) to allow increasing data buffering capabilities within a sessiondespite having end nodes with small buffer sizes, e.g., typically 16 kbytes. However, RFC 1323 requires window scaling for any buffer sizesgreater than 64 k bytes, which can be set at the time of sessioninitialization (SYN, SYN-ACK signals). Moreover, the window scalingcorresponds to the lowest common denominator in the data path, often anend node with small buffer size. This window scale often is a scale of 0or 1, which corresponds to a buffer size of up to 64 k or 128 k bytes.Note that because the window size is defined as the window field in eachpacket shifted over by the window scale, the window scale establishes anupper limit for the buffer, but does not guarantee the buffer isactually that large. Each packet indicates the current available bufferspace at the receiver in the window field.

In one embodiment of scaling using the window virtualization technique,during connection establishment (i.e., initialization of a session) whenthe first flow control module 220 receives from the source node 102 theSYN signal (or packet), the flow control module 220 stores the windowsscale of the source node 102 (which is the previous node) or stores a 0for window scale if the scale of the previous node is missing. The firstflow control module 220 also modifies the scale, e.g., increases thescale to 4 from 0 or 1, in the SYN-FCM signal. When the second flowcontrol module 220 receives the SYN signal, it stores the increasedscale from the first flow control signal and resets the scale in the SYNsignal back to the source node 103 scale value for transmission to thedestination node 106. When the second flow controller 220 receives theSYN-ACK signal from the destination node 106, it stores the scale fromthe destination node 106 scale, e.g., 0 or 1, and modifies it to anincreased scale that is sent with the SYN-ACK-FCM signal. The first flowcontrol node 220 receives and notes the received window scale andrevises the windows scale sent back to the source node 102 back down tothe original scale, e.g., 0 or 1. Based on the above window shiftconversation during connection establishment, the window field in everysubsequent packet, e.g., TCP packet, of the session can be shiftedaccording to the window shift conversion.

The window scale, as described above, expresses buffer sizes of over 64k and may not be required for window virtualization. Thus, shifts forwindow scale may be used to express increased buffer capacity in eachflow control module 220. This increase in buffer capacity in may bereferenced as window (or buffer) virtualization. The increase in buffersize allows greater packet through put from and to the respective endnodes 102 and 106. Note that buffer sizes in TCP are typically expressedin terms of bytes, but for ease of discussion “packets” may be used inthe description herein as it relates to virtualization.

By way of example, a window (or buffer) virtualization performed by theflow controller 220 is described. In this example, the source node 102and the destination node 106 are configured similar to conventional endnodes having a limited buffer capacity of 16 k bytes, which equalsapproximately 10 packets of data. Typically, an end node 102, 106 canwait until the packet is transmitted and confirmation is received beforea next group of packets can be transmitted. In one embodiment, usingincreased buffer capacity in the flow control modules 220, when thesource node 103 transmits its data packets, the first flow controlmodule 220 receives the packets, stores it in its larger capacitybuffer, e.g., 512 packet capacity, and immediately sends back anacknowledgement signal indicating receipt of the packets (“REC-ACK”)back to the source node 102. The source node 102 can then “flush” itscurrent buffer, load it with 10 new data packets, and transmit thoseonto the first flow control module 220. Again, the first flow controlmodule 220 transmits a REC-ACK signal back to the source node 102 andthe source node 102 flushes its buffer and loads it with 10 more newpackets for transmission.

As the first flow control module 220 receives the data packets from thesource nodes, it loads up its buffer accordingly. When it is ready thefirst flow control module 220 can begin transmitting the data packets tothe second flow control module 230, which also has an increased buffersize, for example, to receive 512 packets. The second flow controlmodule 220′ receives the data packets and begins to transmit 10 packetsat a time to the destination node 106. Each REC-ACK received at thesecond flow control node 220 from the destination node 106 results in 10more packets being transmitted to the destination node 106 until all thedata packets are transferred. Hence, the present disclosure is able toincrease data transmission throughput between the source node (sender)102 and the destination node (receiver) 106 by taking advantage of thelarger buffer in the flow control modules 220, 220′ between the devices.

It is noted that by “preacking” the transmission of data as describedpreviously, a sender (or source node 102) is allowed to transmit moredata than is possible without the preacks, thus affecting a largerwindow size. For example, in one embodiment this technique is effectivewhen the flow control module 220, 220′ is located “near” a node (e.g.,source node 102 or destination node 106) that lacks large windows.

Recongestion

Another technique or algorithm of the flow controller 220 is referred toas recongestion. The standard TCP congestion avoidance algorithms areknown to perform poorly in the face of certain network conditions,including: large RTTs (round trip times), high packet loss rates, andothers. When the appliance 200 detects a congestion condition such aslong round trip times or high packet loss, the appliance 200 intervenes,substituting an alternate congestion avoidance algorithm that bettersuits the particular network condition. In one embodiment, therecongestion algorithm uses preacks to effectively terminate theconnection between the sender and the receiver. The appliance 200 thenresends the packets from itself to the receiver, using a differentcongestion avoidance algorithm. Recongestion algorithms may be dependenton the characteristics of the TCP connection. The appliance 200 monitorseach TCP connection, characterizing it with respect to the differentdimensions, selecting a recongestion algorithm that is appropriate forthe current characterization.

In one embodiment, upon detecting a TCP connection that is limited byround trip times (RTT), a recongestion algorithm is applied whichbehaves as multiple TCP connections. Each TCP connection operates withinits own performance limit but the aggregate bandwidth achieves a higherperformance level. One parameter in this mechanism is the number ofparallel connections that are applied (N). Too large a value of N andthe connection bundle achieves more than its fair share of bandwidth.Too small a value of N and the connection bundle achieves less than itsfair share of bandwidth. One method of establishing “N” relies on theappliance 200 monitoring the packet loss rate, RTT, and packet size ofthe actual connection. These numbers are plugged into a TCP responsecurve formula to provide an upper limit on the performance of a singleTCP connection in the present configuration. If each connection withinthe connection bundle is achieving substantially the same performance asthat computed to be the upper limit, then additional parallelconnections are applied. If the current bundle is achieving lessperformance than the upper limit, the number of parallel connections isreduced. In this manner, the overall fairness of the system ismaintained since individual connection bundles contain no moreparallelism than is required to eliminate the restrictions imposed bythe protocol itself. Furthermore, each individual connection retains TCPcompliance.

Another method of establishing “N” is to utilize a parallel flow controlalgorithm such as the TCP “Vegas” algorithm or its improved version“Stabilized Vegas.” In this method, the network information associatedwith the connections in the connection bundle (e.g., RTT, loss rate,average packet size, etc.) is aggregated and applied to the alternateflow control algorithm. The results of this algorithm are in turndistributed among the connections of the bundle controlling their number(i.e., N). Optionally, each connection within the bundle continues usingthe standard TCP congestion avoidance algorithm.

In another embodiment, the individual connections within a parallelbundle are virtualized, i.e., actual individual TCP connections are notestablished. Instead the congestion avoidance algorithm is modified tobehave as though there were N parallel connections. This method has theadvantage of appearing to transiting network nodes as a singleconnection. Thus the QOS, security and other monitoring methods of thesenodes are unaffected by the recongestion algorithm. In yet anotherembodiment, the individual connections within a parallel bundle arereal, i.e., a separate. TCP connection is established for each of theparallel connections within a bundle. The congestion avoidance algorithmfor each TCP connection need not be modified.

Retransmission

In some embodiments, the flow controller 220 may apply a localretransmission technique. One reason for implementing preacks is toprepare to transit a high-loss link (e.g., wireless). In theseembodiments, the preacking appliance 200 or flow control module 220 islocated most beneficially “before” the wireless link. This allowsretransmissions to be performed closer to the high loss link, removingthe retransmission burden from the remainder of the network. Theappliance 200 may provide local retransmission, in which case, packetsdropped due to failures of the link are retransmitted directly by theappliance 200. This is advantageous because it eliminates theretransmission burden upon an end node, such as server 106, andinfrastructure of any of the networks 104. With appliance 200 providinglocal retransmissions, the dropped packet can be retransmitted acrossthe high loss link without necessitating a retransmit by an end node anda corresponding decrease in the rate of data transmission from the endnode.

Another reason for implementing preacks is to avoid a receive time out(RTO) penalty. In standard TCP there are many situations that result inan RTO, even though a large percentage of the packets in flight weresuccessfully received. With standard TCP algorithms, dropping more thanone packet within an RTT window would likely result in a timeout.Additionally, most TCP connections experience a timeout if aretransmitted packet is dropped. In a network with a high bandwidthdelay product, even a relatively small packet loss rate will causefrequent Retransmission timeouts (RTOs). In one embodiment, theappliance 200 uses a retransmit and timeout algorithm is avoid prematureRTOs. The appliance 200 or flow controller 220 maintains a count ofretransmissions is maintained on a per-packet basis. Each time that apacket is retransmitted, the count is incremented by one and theappliance 200 continues to transmit packets. In some embodiments, onlyif a packet has been retransmitted a predetermined number of times is anRTO declared.

Wavefront Detection and Disambiguation

In some embodiments, the appliance 200 or flow controller 220 useswavefront detection and disambiguation techniques in managing andcontrolling flow of network traffic. In this technique, the flowcontroller 220 uses transmit identifiers or numbers to determine whetherparticular data packets need to be retransmitted. By way of example, asender transmits data packets over a network, where each instance of atransmitted data packet is associated with a transmit number. It can beappreciated that the transmit number for a packet is not the same as thepacket's sequence number, since a sequence number references the data inthe packet while the transmit number references an instance of atransmission of that data. The transmit number can be any informationusable for this purpose, including a timestamp associated with a packetor simply an increasing number (similar to a sequence number or a packetnumber). Because a data segment may be retransmitted, different transmitnumbers may be associated with a particular sequence number.

As the sender transmits data packets, the sender maintains a datastructure of acknowledged instances of data packet transmissions. Eachinstance of a data packet transmission is referenced by its sequencenumber and transmit number. By maintaining a transmit number for eachpacket, the sender retains the ordering of the transmission of datapackets. When the sender receives an ACK or a SACK, the senderdetermines the highest transmit number associated with packets that thereceiver indicated has arrived (in the received acknowledgement). Anyoutstanding unacknowledged packets with lower transmit numbers arepresumed lost.

In some embodiments, the sender is presented with an ambiguous situationwhen the arriving packet has been retransmitted: a standard ACK/SACKdoes not contain enough information to allow the sender to determinewhich transmission of the arriving packet has triggered theacknowledgement. After receiving an ambiguous acknowledgement,therefore, the sender disambiguates the acknowledgement to associate itwith a transmit number. In various embodiments, one or a combination ofseveral techniques may be used to resolve this ambiguity.

In one embodiment, the sender includes an identifier with a transmitteddata packet, and the receiver returns that identifier or a functionthereof with the acknowledgement. The identifier may be a timestamp(e.g., a TCP timestamp as described in RFC 1323), a sequential number,or any other information that can be used to resolve between two or moreinstances of a packet's transmission. In an embodiment in which the TCPtimestamp option is used to disambiguate the acknowledgement, eachpacket is tagged with up to 32-bits of unique information. Upon receiptof the data packet, the receiver echoes this unique information back tothe sender with the acknowledgement. The sender ensures that theoriginally sent packet and its retransmitted version or versions containdifferent values for the timestamp option, allowing it to unambiguouslyeliminate the ACK ambiguity. The sender may maintain this uniqueinformation, for example, in the data structure in which it stores thestatus of sent data packets. This technique is advantageous because itcomplies with industry standards and is thus likely to encounter littleor no interoperability issues. However, this technique may require tenbytes of TCP header space in some implementations, reducing theeffective throughput rate on the network and reducing space availablefor other TCP options.

In another embodiment, another field in the packet, such as the IP IDfield, is used to disambiguate in a way similar to the TCP timestampoption described above. The sender arranges for the ID field values ofthe original and the retransmitted version or versions of the packet tohave different ID fields in the IP header. Upon reception of the datapacket at the receiver, or a proxy device thereof, the receiver sets theID field of the ACK packet to a function of the ID field of the packetthat triggers the ACK. This method is advantageous, as it requires noadditional data to be sent, preserving the efficiency of the network andTCP header space. The function chosen should provide a high degree oflikelihood of providing disambiguation. In a preferred embodiment, thesender selects IP ID values with the most significant bit set to 0. Whenthe receiver responds, the IP ID value is set to the same IP ID valuewith the most significant bit set to a one.

In another embodiment, the transmit numbers associated withnon-ambiguous acknowledgements are used to disambiguate an ambiguousacknowledgement. This technique is based on the principle thatacknowledgements for two packets will tend to be received closer in timeas the packets are transmitted closer in time. Packets that are notretransmitted will not result in ambiguity, as the acknowledgementsreceived for such packets can be readily associated with a transmitnumber. Therefore, these known transmit numbers are compared to thepossible transmit numbers for an ambiguous acknowledgement received nearin time to the known acknowledgement. The sender compares the transmitnumbers of the ambiguous acknowledgement against the last known receivedtransmit number, selecting the one closest to the known receivedtransmit number. For example, if an acknowledgement for data packet 1 isreceived and the last received acknowledgement was for data packet 5,the sender resolves the ambiguity by assuming that the third instance ofdata packet 1 caused the acknowledgement.

Selective Acknowledgements

Another technique of the appliance 200 or flow controller 220 is toimplement an embodiment of transport control protocol selectiveacknowledgements, or TCP SACK, to determine what packets have or havenot been received. This technique allows the sender to determineunambiguously a list of packets that have been received by the receiveras well as an accurate list of packets not received. This functionalitymay be implemented by modifying the sender and/or receiver, or byinserting sender- and receiver-side flow control modules 220 in thenetwork path between the sender and receiver. In reference to FIG. 1A orFIG. 1B, a sender, e.g., client 102, is configured to transmit datapackets to the receiver, e.g., server 106, over the network 104. Inresponse, the receiver returns a TCP Selective Acknowledgment option,referred to as SACK packet to the sender. In one embodiment, thecommunication is bi-directional, although only one direction ofcommunication is discussed here for simplicity. The receiver maintains alist, or other suitable data structure, that contains a group of rangesof sequence numbers for data packets that the receiver has actuallyreceived. In some embodiments, the list is sorted by sequence number inan ascending or descending order. The receiver also maintains a left-offpointer, which comprises a reference into the list and indicates theleft-off point from the previously generated SACK packet.

Upon reception of a data packet, the receiver generates and transmits aSACK packet back to the sender. In some embodiments, the SACK packetincludes a number of fields, each of which can hold a range of sequencenumbers to indicate a set of received data packets. The receiver fillsthis first field of the SACK packet with a range of sequence numbersthat includes the landing packet that triggered the SACK packet. Theremaining available SACK fields are filled with ranges of sequencenumbers from the list of received packets. As there are more ranges inthe list than can be loaded into the SACK packet, the receiver uses theleft-off pointer to determine which ranges are loaded into the SACKpacket. The receiver inserts the SACK ranges consecutively from thesorted list, starting from the range referenced by the pointer andcontinuing down the list until the available SACK range space in the TCPheader of the SACK packet is consumed. The receiver wraps around to thestart of the list if it reaches the end. In some embodiments, two orthree additional SACK ranges can be added to the SACK range information.

Once the receiver generates the SACK packet, the receiver sends theacknowledgement back to the sender. The receiver then advances theleft-off pointer by one or more SACK range entries in the list. If thereceiver inserts four SACK ranges, for example, the left-off pointer maybe advanced two SACK ranges in the list. When the advanced left-offpointer reaches at the end of the list, the pointer is reset to thestart of the list, effectively wrapping around the list of knownreceived ranges. Wrapping around the list enables the system to performwell, even in the presence of large losses of SACK packets, since theSACK information that is not communicated due to a lost SACK packet willeventually be communicated once the list is wrapped around.

It can be appreciated, therefore, that a SACK packet may communicateseveral details about the condition of the receiver. First, the SACKpacket indicates that, upon generation of the SACK packet, the receiverhad just received a data packet that is within the first field of theSACK information. Secondly, the second and subsequent fields of the SACKinformation indicate that the receiver has received the data packetswithin those ranges. The SACK information also implies that the receiverhad not, at the time of the SACK packet's generation, received any ofthe data packets that fall between the second and subsequent fields ofthe SACK information. In essence, the ranges between the second andsubsequent ranges in the SACK information are “holes” in the receiveddata, the data therein known not to have been delivered. Using thismethod, therefore, when a SACK packet has sufficient space to includemore than two SACK ranges, the receiver may indicate to the sender arange of data packets that have not yet been received by the receiver.

In another embodiment, the sender uses the SACK packet described abovein combination with the retransmit technique described above to makeassumptions about which data packets have been delivered to thereceiver. For example, when the retransmit algorithm (using the transmitnumbers) declares a packet lost, the sender considers the packet to beonly conditionally lost, as it is possible that the SACK packetidentifying the reception of this packet was lost rather than the datapacket itself. The sender thus adds this packet to a list of potentiallylost packets, called the presumed lost list. Each time a SACK packetarrives, the known missing ranges of data from the SACK packet arecompared to the packets in the presumed lost list. Packets that containdata known to be missing are declared actually lost and are subsequentlyretransmitted. In this way, the two schemes are combined to give thesender better information about which packets have been lost and need tobe retransmitted.

Transaction Boundary Detection

In some embodiments, the appliance 200 or flow controller 220 applies atechnique referred to as transaction boundary detection. In oneembodiment, the technique pertains to ping-pong behaved connections. Atthe TCP layer, ping-pong behavior is when one communicant—a sender—sendsdata and then waits for a response from the other communicant—thereceiver. Examples of ping-pong behavior include remote procedure call,HTTP and others. The algorithms described above use retransmissiontimeout (RTO) to recover from the dropping of the last packet or packetsassociated with the transaction. Since the TCP RTO mechanism isextremely coarse in some embodiments, for example requiring a minimumone second value in all cases), poor application behavior may be seen inthese situations.

In one embodiment, the sender of data or a flow control module 220coupled to the sender detects a transaction boundary in the data beingsent. Upon detecting a transaction boundary, the sender or a flowcontrol module 220 sends additional packets, whose reception generatesadditional ACK or SACK responses from the receiver. Insertion of theadditional packets is preferably limited to balance between improvedapplication response time and network capacity utilization. The numberof additional packets that is inserted may be selected according to thecurrent loss rate associated with that connection, with more packetsselected for connections having a higher loss rate.

One method of detecting a transaction boundary is time based. If thesender has been sending data and ceases, then after a period of time thesender or flow control module 200 declares a transaction boundary. Thismay be combined with other techniques. For example, the setting of thePSH (TCP Push) bit by the sender in the TCP header may indicate atransaction boundary. Accordingly, combining the time-based approachwith these additional heuristics can provide for more accurate detectionof a transaction boundary. In another technique, if the sender or flowcontrol module 220 understands the application protocol, it can parsethe protocol data stream and directly determine transaction boundaries.In some embodiment, this last behavior can be used independent of anytime-based mechanism.

Responsive to detecting a transaction boundary, the sender or flowcontrol module 220 transmits additional data packets to the receiver tocause acknowledgements therefrom. The additional data packets shouldtherefore be such that the receiver will at least generate an ACK orSACK in response to receiving the data packet. In one embodiment, thelast packet or packets of the transaction are simply retransmitted. Thishas the added benefit of retransmitting needed data if the last packetor packets had been dropped, as compared to merely sending dummy datapackets. In another embodiment, fractions of the last packet or packetsare sent, allowing the sender to disambiguate the arrival of thesepackets from their original packets. This allows the receiver to avoidfalsely confusing any reordering adaptation algorithms. In anotherembodiment, any of a number of well-known forward error correctiontechniques can be used to generate additional data for the insertedpackets, allowing for the reconstruction of dropped or otherwise missingdata at the receiver.

In some embodiments, the boundary detection technique described hereinhelps to avoid a timeout when the acknowledgements for the last datapackets in a transaction are dropped. When the sender or flow controlmodule 220 receives the acknowledgements for these additional datapackets, the sender can determine from these additional acknowledgementswhether the last data packets have been received or need to beretransmitted, thus avoiding a timeout. In one embodiment, if the lastpackets have been received but their acknowledgements were dropped, aflow control module 220 generates an acknowledgement for the datapackets and sends the acknowledgement to the sender, thus communicatingto the sender that the data packets have been delivered. In anotherembodiment, if the last packets have not been received, a flow controlmodule 200 sends a packet to the sender to cause the sender toretransmit the dropped data packets.

Repacketization

In yet another embodiment, the appliance 200 or flow controller 220applies a repacketization technique for improving the flow of transportlayer network traffic. In some embodiments, performance of TCP isproportional to packet size. Thus increasing packet sizes improvesperformance unless it causes substantially increased packet loss ratesor other nonlinear effects, like IP fragmentation. In general, wiredmedia (such as copper or fibre optics) have extremely low bit-errorrates, low enough that these can be ignored. For these media, it isadvantageous for the packet size to be the maximum possible beforefragmentation occurs (the maximum packet size is limited by theprotocols of the underlying transmission media). Whereas fortransmission media with higher loss rates (e.g., wireless technologiessuch as WiFi, etc., or high-loss environments such as power-linenetworking, etc.), increasing the packet size may lead to lowertransmission rates, as media-induced errors cause an entire packet to bedropped (i.e., media-induced errors beyond the capability of thestandard error correcting code for that media), increasing the packetloss rate. A sufficiently large increase in the packet loss rate willactually negate any performance benefit of increasing packet size. Insome cases, it may be difficult for a TCP endpoint to choose an optimalpacket size. For example, the optimal packet size may vary across thetransmission path, depending on the nature of each link.

By inserting an appliance 200 or flow control module 220 into thetransmission path, the flow controller 220 monitors characteristics ofthe link and repacketizes according to determined link characteristics.In one embodiment, an appliance 200 or flow controller 220 repacketizespackets with sequential data into a smaller number of larger packets. Inanother embodiment, an appliance 200 or flow controller 220 repacketizespackets by breaking part a sequence of large packets into a largernumber of smaller packets. In other embodiments, an appliance 200 orflow controller 220 monitors the link characteristics and adjusts thepacket sizes through recombination to improve throughput.

Quality of Service (“QoS”)

Still referring to FIG. 2A, the flow controller 220, in someembodiments, may include a QoS Engine 236, also referred to as a QoScontroller. In another embodiment, the appliance 200 and/or networkoptimization engine 250 includes the QoS engine 236, for example,separately but in communication with the flow controller 220. The QoSEngine 236 includes any logic, business rules, function or operationsfor performing one or more Quality of Service (QoS) techniques improvingthe performance, operation or quality of service of any of the networkconnections. In some embodiments, the QoS engine 236 includes networktraffic control and management mechanisms that provide differentpriorities to different users, applications, data flows or connections.In other embodiments, the QoS engine 236 controls, maintains, or assuresa certain level of performance to a user, application, data flow orconnection. In one embodiment, the QoS engine 236 controls, maintains orassures a certain portion of bandwidth or network capacity for a user,application, data flow or connection. In some embodiments, the QoSengine 236 monitors the achieved level of performance or the quality ofservice corresponding to a user, application, data flow or connection,for example, the data rate and delay. In response to monitoring, the QoSengine 236 dynamically controls or adjusts scheduling priorities ofnetwork packets to achieve the desired level of performance or qualityof service.

In some embodiments, the QoS engine 236 prioritizes, schedules andtransmits network packets according to one or more classes or levels ofservices. In some embodiments, the class or level service mayinclude: 1) best efforts, 2) controlled load, 3) guaranteed or 4)qualitative. For a best efforts class of service, the appliance 200makes reasonable effort to deliver packets (a standard service level).For a controlled load class of service, the appliance 200 or QoS engine236 approximates the standard packet error loss of the transmissionmedium or approximates the behavior of best-effort service in lightlyloaded network conditions. For a guaranteed class of service, theappliance 200 or QoS engine 236 guarantees the ability to transmit dataat a determined rate for the duration of the connection. For aqualitative class of service, the appliance 200 or QoS engine 236 thequalitative service class is used for applications, users, data flows orconnection that require or desire prioritized traffic but cannotquantify resource needs or level of service. In these cases, theappliance 200 or QoS engine 236 determines the class of service orprioritization based on any logic or configuration of the QoS engine 236or based on business rules or policies. For example, in one embodiment,the QoS engine 236 prioritizes, schedules and transmits network packetsaccording to one or more policies as specified by the policy engine 295,295′.

Protocol Acceleration

The protocol accelerator 234 includes any logic, business rules,function or operations for optimizing, accelerating, or otherwiseimproving the performance, operation or quality of service of one ormore protocols. In one embodiment, the protocol accelerator 234accelerates any application layer protocol or protocols at layers 5-7 ofthe network stack. In other embodiments, the protocol accelerator 234accelerates a transport layer or a layer 4 protocol. In one embodiment,the protocol accelerator 234 accelerates layer 2 or layer 3 protocols.In some embodiments, the protocol accelerator 234 is configured,constructed or designed to optimize or accelerate each of one or moreprotocols according to the type of data, characteristics and/or behaviorof the protocol. In another embodiment, the protocol accelerator 234 isconfigured, constructed or designed to improve a user experience,response times, network or computer load, and/or network or bandwidthutilization with respect to a protocol.

In one embodiment, the protocol accelerator 234 is configured,constructed or designed to minimize the effect of WAN latency on filesystem access. In some embodiments, the protocol accelerator 234optimizes or accelerates the use of the CIFS (Common Internet FileSystem) protocol to improve file system access times or access times todata and files. In some embodiments, the protocol accelerator 234optimizes or accelerates the use of the NFS (Network File System)protocol. In another embodiment, the protocol accelerator 234 optimizesor accelerates the use of the File Transfer protocol (FTP).

In one embodiment, the protocol accelerator 234 is configured,constructed or designed to optimize or accelerate a protocol carrying asa payload or using any type and form of markup language. In otherembodiments, the protocol accelerator 234 is configured, constructed ordesigned to optimize or accelerate a HyperText Transfer Protocol (HTTP).In another embodiment, the protocol accelerator 234 is configured,constructed or designed to optimize or accelerate a protocol carrying asa payload or otherwise using XML (eXtensible Markup Language).

Transparency and Multiple Deployment Configuration

In some embodiments, the appliance 200 and/or network optimizationengine 250 is transparent to any data flowing across a networkconnection or link, such as a WAN link. In one embodiment, the appliance200 and/or network optimization engine 250 operates in such a mannerthat the data flow across the WAN is recognizable by any networkmonitoring, QOS management or network analysis tools. In someembodiments, the appliance 200 and/or network optimization engine 250does not create any tunnels or streams for transmitting data that mayhide, obscure or otherwise make the network traffic not transparent. Inother embodiments, the appliance 200 operates transparently in that theappliance does not change any of the source and/or destination addressinformation or port information of a network packet, such as internetprotocol addresses or port numbers. In other embodiments, the appliance200 and/or network optimization engine 250 is considered to operate orbehave transparently to the network, an application, client, server orother appliances or computing device in the network infrastructure. Thatis, in some embodiments, the appliance is transparent in that networkrelated configuration of any device or appliance on the network does notneed to be modified to support the appliance 200.

The appliance 200 may be deployed in any of the following deploymentconfigurations: 1) in-line of traffic, 2) in proxy mode, or 3) in avirtual in-line mode. In some embodiments, the appliance 200 may bedeployed inline to one or more of the following: a router, a client, aserver or another network device or appliance. In other embodiments, theappliance 200 may be deployed in parallel to one or more of thefollowing: a router, a client, a server or another network device orappliance. In parallel deployments, a client, server, router or othernetwork appliance may be configured to forward, transfer or transitnetworks to or via the appliance 200.

In the embodiment of in-line, the appliance 200 is deployed seriallywith a WAN link of a router. In this way, all traffic from the WANpasses through the appliance before arriving at a destination of a LAN.

In the embodiment of a proxy mode, the appliance 200 is deployed as aproxy device between a client and a server. In some embodiments, theappliance 200 allows clients to make indirect connections to a resourceon a network. For example, a client connects to a resource via theappliance 200, and the appliance provides the resource either byconnecting to the resource, a different resource, or by serving theresource from a cache. In some cases, the appliance may alter theclient's request or the server's response for various purposes, such asfor any of the optimization techniques discussed herein. In otherembodiments, the appliance 200 behaves as a transparent proxy, byintercepting and forwarding requests and responses transparently to aclient and/or server. Without client-side configuration, the appliance200 may redirect client requests to different servers or networks. Insome embodiments, the appliance 200 may perform any type and form ofnetwork address translation, referred to as NAT, on any network traffictraversing the appliance.

In some embodiments, the appliance 200 is deployed in a virtual in-linemode configuration. In this embodiment, a router or a network devicewith routing or switching functionality is configured to forward,reroute or otherwise provide network packets destined to a network tothe appliance 200. The appliance 200 then performs any desiredprocessing on the network packets, such as any of the WAN optimizationtechniques discussed herein. Upon completion of processing, theappliance 200 forwards the processed network packet to the router totransmit to the destination on the network. In this way, the appliance200 can be coupled to the router in parallel but still operate as it ifthe appliance 200 were inline. This deployment mode also providestransparency in that the source and destination addresses and portinformation are preserved as the packet is processed and transmitted viathe appliance through the network.

End Node Deployment

Although the network optimization engine 250 is generally describedabove in conjunction with an appliance 200, the network optimizationengine 250, or any portion thereof, may be deployed, distributed orotherwise operated on any end node, such as a client 102 and/or server106. As such, a client or server may provide any of the systems andmethods of the network optimization engine 250 described herein inconjunction with one or more appliances 200 or without an appliance 200.

Referring now to FIG. 2B, an example embodiment of the networkoptimization engine 250 deployed on one or more end nodes is depicted.In brief overview, the client 102 may include a first networkoptimization engine 250′ and the server 106 may include a second networkoptimization engine 250″. The client 102 and server 106 may establish atransport layer connection and exchange communications with or withouttraversing an appliance 200.

In one embodiment, the network optimization engine 250′ of the client102 performs the techniques described herein to optimize, accelerate orotherwise improve the performance, operation or quality of service ofnetwork traffic communicated with the server 106. In another embodiment,the network optimization engine 250″ of the server 106 performs thetechniques described herein to optimize, accelerate or otherwise improvethe performance, operation or quality of service of network trafficcommunicated with the client 102. In some embodiments, the networkoptimization engine 250′ of the client 102 and the network optimizationengine 250″ of the server 106 perform the techniques described herein tooptimize, accelerate or otherwise improve the performance, operation orquality of service of network traffic communicated between the client102 and the server 106. In yet another embodiment, the networkoptimization engine 250′ of the client 102 performs the techniquesdescribed herein in conjunction with an appliance 200 to optimize,accelerate or otherwise improve the performance, operation or quality ofservice of network traffic communicated with the client 102. In stillanother embodiment, the network optimization engine 250″ of the server106 performs the techniques described herein in conjunction with anappliance 200 to optimize, accelerate or otherwise improve theperformance, operation or quality of service of network trafficcommunicated with the server 106.

C: Client Agent

Referring now to FIG. 3, an embodiment of a client agent 120 isdepicted. The client 102 has a client agent 120 for establishing,exchanging, managing or controlling communications with the appliance200, appliance 205 and/or server 106 via a network 104. In someembodiments, the client agent 120, which may also be referred to as aWAN client, accelerates WAN network communications and/or is used tocommunicate via appliance 200 on a network. In brief overview, theclient 102 operates on computing device 100 having an operating systemwith a kernel mode 302 and a user mode 303, and a network stack 267 withone or more layers 310 a-310 b. The client 102 may have installed and/orexecute one or more applications. In some embodiments, one or moreapplications may communicate via the network stack 267 to a network 104.One of the applications, such as a web browser, may also include a firstprogram 322. For example, the first program 322 may be used in someembodiments to install and/or execute the client agent 120, or anyportion thereof. The client agent 120 includes an interceptionmechanism, or interceptor 350, for intercepting network communicationsfrom the network stack 267 from the one or more applications.

As with the appliance 200, the client has a network stack 267 includingany type and form of software, hardware, or any combinations thereof,for providing connectivity to and communications with a network 104. Thenetwork stack 267 of the client 102 includes any of the network stackembodiments described above in conjunction with the appliance 200. Insome embodiments, the client agent 120, or any portion thereof, isdesigned and constructed to operate with or work in conjunction with thenetwork stack 267 installed or otherwise provided by the operatingsystem of the client 102.

In further details, the network stack 267 of the client 102 or appliance200 (or 205) may include any type and form of interfaces for receiving,obtaining, providing or otherwise accessing any information and datarelated to network communications of the client 102. In one embodiment,an interface to the network stack 267 includes an applicationprogramming interface (API). The interface may also have any functioncall, hooking or filtering mechanism, event or call back mechanism, orany type of interfacing technique. The network stack 267 via theinterface may receive or provide any type and form of data structure,such as an object, related to functionality or operation of the networkstack 267. For example, the data structure may include information anddata related to a network packet or one or more network packets. In someembodiments, the data structure includes, references or identifies aportion of the network packet processed at a protocol layer of thenetwork stack 267, such as a network packet of the transport layer. Insome embodiments, the data structure 325 is a kernel-level datastructure, while in other embodiments, the data structure 325 is auser-mode data structure. A kernel-level data structure may have a datastructure obtained or related to a portion of the network stack 267operating in kernel-mode 302, or a network driver or other softwarerunning in kernel-mode 302, or any data structure obtained or receivedby a service, process, task, thread or other executable instructionsrunning or operating in kernel-mode of the operating system.

Additionally, some portions of the network stack 267 may execute oroperate in kernel-mode 302, for example, the data link or network layer,while other portions execute or operate in user-mode 303, such as anapplication layer of the network stack 267. For example, a first portion310 a of the network stack may provide user-mode access to the networkstack 267 to an application while a second portion 310 a of the networkstack 267 provides access to a network. In some embodiments, a firstportion 310 a of the network stack has one or more upper layers of thenetwork stack 267, such as any of layers 5-7. In other embodiments, asecond portion 310 b of the network stack 267 includes one or more lowerlayers, such as any of layers 1-4. Each of the first portion 310 a andsecond portion 310 b of the network stack 267 may include any portion ofthe network stack 267, at any one or more network layers, in user-mode303, kernel-mode 302, or combinations thereof, or at any portion of anetwork layer or interface point to a network layer or any portion of orinterface point to the user-mode 302 and kernel-mode 203.

The interceptor 350 may include software, hardware, or any combinationof software and hardware. In one embodiment, the interceptor 350intercepts or otherwise receives a network communication at any point inthe network stack 267, and redirects or transmits the networkcommunication to a destination desired, managed or controlled by theinterceptor 350 or client agent 120. For example, the interceptor 350may intercept a network communication of a network stack 267 of a firstnetwork and transmit the network communication to the appliance 200 fortransmission on a second network 104. In some embodiments, theinterceptor 350 includes or is a driver, such as a network driverconstructed and designed to interface and work with the network stack267. In some embodiments, the client agent 120 and/or interceptor 350operates at one or more layers of the network stack 267, such as at thetransport layer. In one embodiment, the interceptor 350 includes afilter driver, hooking mechanism, or any form and type of suitablenetwork driver interface that interfaces to the transport layer of thenetwork stack, such as via the transport driver interface (TDI). In someembodiments, the interceptor 350 interfaces to a first protocol layer,such as the transport layer and another protocol layer, such as anylayer above the transport protocol layer, for example, an applicationprotocol layer. In one embodiment, the interceptor 350 includes a drivercomplying with the Network Driver Interface Specification (NDIS), or aNDIS driver. In another embodiment, the interceptor 350 may be amin-filter or a mini-port driver. In one embodiment, the interceptor350, or portion thereof, operates in kernel-mode 202. In anotherembodiment, the interceptor 350, or portion thereof, operates inuser-mode 203. In some embodiments, a portion of the interceptor 350operates in kernel-mode 202 while another portion of the interceptor 350operates in user-mode 203. In other embodiments, the client agent 120operates in user-mode 203 but interfaces via the interceptor 350 to akernel-mode driver, process, service, task or portion of the operatingsystem, such as to obtain a kernel-level data structure 225. In furtherembodiments, the interceptor 350 is a user-mode application or program,such as application.

In one embodiment, the interceptor 350 intercepts or receives anytransport layer connection requests. In these embodiments, theinterceptor 350 executes transport layer application programminginterface (API) calls to set the destination information, such asdestination IP address and/or port to a desired location for thelocation. In this manner, the interceptor 350 intercepts and redirectsthe transport layer connection to an IP address and port controlled ormanaged by the interceptor 350 or client agent 120. In one embodiment,the interceptor 350 sets the destination information for the connectionto a local IP address and port of the client 102 on which the clientagent 120 is listening. For example, the client agent 120 may comprise aproxy service listening on a local IP address and port for redirectedtransport layer communications. In some embodiments, the client agent120 then communicates the redirected transport layer communication tothe appliance 200.

In some embodiments, the interceptor 350 intercepts a Domain NameService (DNS) request. In one embodiment, the client agent 120 and/orinterceptor 350 resolves the DNS request. In another embodiment, theinterceptor transmits the intercepted DNS request to the appliance 200for DNS resolution. In one embodiment, the appliance 200 resolves theDNS request and communicates the DNS response to the client agent 120.In some embodiments, the appliance 200 resolves the DNS request viaanother appliance 200′ or a DNS server 106.

In yet another embodiment, the client agent 120 may include two agents120 and 120′. In one embodiment, a first agent 120 may include aninterceptor 350 operating at the network layer of the network stack 267.In some embodiments, the first agent 120 intercepts network layerrequests such as Internet Control Message Protocol (ICMP) requests(e.g., ping and traceroute). In other embodiments, the second agent 120′may operate at the transport layer and intercept transport layercommunications. In some embodiments, the first agent 120 interceptscommunications at one layer of the network stack 210 and interfaces withor communicates the intercepted communication to the second agent 120′.

The client agent 120 and/or interceptor 350 may operate at or interfacewith a protocol layer in a manner transparent to any other protocollayer of the network stack 267. For example, in one embodiment, theinterceptor 350 operates or interfaces with the transport layer of thenetwork stack 267 transparently to any protocol layer below thetransport layer, such as the network layer, and any protocol layer abovethe transport layer, such as the session, presentation or applicationlayer protocols. This allows the other protocol layers of the networkstack 267 to operate as desired and without modification for using theinterceptor 350. As such, the client agent 120 and/or interceptor 350can interface with the transport layer to secure, optimize, accelerate,route or load-balance any communications provided via any protocolcarried by the transport layer, such as any application layer protocolover TCP/IP.

Furthermore, the client agent 120 and/or interceptor 350 may operate ator interface with the network stack 267 in a manner transparent to anyapplication, a user of the client 102, the client 102 and/or any othercomputing device 100, such as a server or appliance 200, 206, incommunications with the client 102. The client agent 120, or any portionthereof, may be installed and/or executed on the client 102 in a mannerwithout modification of an application. In one embodiment, the clientagent 120, or any portion thereof, is installed and/or executed in amanner transparent to any network configuration of the client 102,appliance 200, 205 or server 106. In some embodiments, the client agent120, or any portion thereof, is installed and/or executed withmodification to any network configuration of the client 102, appliance200, 205 or server 106. In one embodiment, the user of the client 102 ora computing device in communications with the client 102 are not awareof the existence, execution or operation of the client agent 12, or anyportion thereof. As such, in some embodiments, the client agent 120and/or interceptor 350 is installed, executed, and/or operatedtransparently to an application, user of the client 102, the client 102,another computing device, such as a server or appliance 200, 2005, orany of the protocol layers above and/or below the protocol layerinterfaced to by the interceptor 350.

The client agent 120 includes a streaming client 306, a collection agent304, SSL VPN agent 308, a network optimization engine 250, and/oracceleration program 302. In one embodiment, the client agent 120 is anIndependent Computing Architecture (ICA) client, or any portion thereof,developed by Citrix Systems, Inc. of Fort Lauderdale, Fla., and is alsoreferred to as an ICA client. In some embodiments, the client agent 120has an application streaming client 306 for streaming an applicationfrom a server 106 to a client 102. In another embodiment, the clientagent 120 includes a collection agent 304 for performing end-pointdetection/scanning and collecting end-point information for theappliance 200 and/or server 106. In some embodiments, the client agent120 has one or more network accelerating or optimizing programs oragents, such as an network optimization engine 250 and an accelerationprogram 302. In one embodiment, the acceleration program 302 acceleratescommunications between client 102 and server 106 via appliance 205′. Insome embodiments, the network optimization engine 250 provides WANoptimization techniques as discussed herein.

The streaming client 306 is an application, program, process, service,task or set of executable instructions for receiving and executing astreamed application from a server 106. A server 106 may stream one ormore application data files to the streaming client 306 for playing,executing or otherwise causing to be executed the application on theclient 102. In some embodiments, the server 106 transmits a set ofcompressed or packaged application data files to the streaming client306. In some embodiments, the plurality of application files arecompressed and stored on a file server within an archive file such as aCAB, ZIP, SIT, TAR, JAR or other archive. In one embodiment, the server106 decompresses, unpackages or unarchives the application files andtransmits the files to the client 102. In another embodiment, the client102 decompresses, unpackages or unarchives the application files. Thestreaming client 306 dynamically installs the application, or portionthereof, and executes the application. In one embodiment, the streamingclient 306 may be an executable program. In some embodiments, thestreaming client 306 may be able to launch another executable program.

The collection agent 304 is an application, program, process, service,task or set of executable instructions for identifying, obtaining and/orcollecting information about the client 102. In some embodiments, theappliance 200 transmits the collection agent 304 to the client 102 orclient agent 120. The collection agent 304 may be configured accordingto one or more policies of the policy engine 236 of the appliance. Inother embodiments, the collection agent 304 transmits collectedinformation on the client 102 to the appliance 200. In one embodiment,the policy engine 236 of the appliance 200 uses the collectedinformation to determine and provide access, authentication andauthorization control of the client's connection to a network 104.

In one embodiment, the collection agent 304 is an end-point detectionand scanning program, which identifies and determines one or moreattributes or characteristics of the client. For example, the collectionagent 304 may identify and determine any one or more of the followingclient-side attributes: 1) the operating system or a version of anoperating system, 2) a service pack of the operating system, 3) arunning service, 4) a running process, and 5) a file. The collectionagent 304 may also identify and determine the presence or version of anyone or more of the following on the client: 1) antivirus software, 2)personal firewall software, 3) anti-spam software, and 4) internetsecurity software. The policy engine 236 may have one or more policiesbased on any one or more of the attributes or characteristics of theclient or client-side attributes.

The SSL VPN agent 308 is an application, program, process, service, taskor set of executable instructions for establishing a Secure Socket Layer(SSL) virtual private network (VPN) connection from a first network 104to a second network 104′, 104″, or a SSL VPN connection from a client102 to a server 106. In one embodiment, the SSL VPN agent 308establishes a SSL VPN connection from a public network 104 to a privatenetwork 104′ or 104″. In some embodiments, the SSL VPN agent 308 worksin conjunction with appliance 205 to provide the SSL VPN connection. Inone embodiment, the SSL VPN agent 308 establishes a first transportlayer connection with appliance 205. In some embodiment, the appliance205 establishes a second transport layer connection with a server 106.In another embodiment, the SSL VPN agent 308 establishes a firsttransport layer connection with an application on the client, and asecond transport layer connection with the appliance 205. In otherembodiments, the SSL VPN agent 308 works in conjunction with WANoptimization appliance 200 to provide SSL VPN connectivity.

In some embodiments, the acceleration program 302 is a client-sideacceleration program for performing one or more acceleration techniquesto accelerate, enhance or otherwise improve a client's communicationswith and/or access to a server 106, such as accessing an applicationprovided by a server 106. The logic, functions, and/or operations of theexecutable instructions of the acceleration program 302 may perform oneor more of the following acceleration techniques: 1) multi-protocolcompression, 2) transport control protocol pooling, 3) transport controlprotocol multiplexing, 4) transport control protocol buffering, and 5)caching via a cache manager. Additionally, the acceleration program 302may perform encryption and/or decryption of any communications receivedand/or transmitted by the client 102. In some embodiments, theacceleration program 302 performs one or more of the accelerationtechniques in an integrated manner or fashion. Additionally, theacceleration program 302 can perform compression on any of theprotocols, or multiple-protocols, carried as a payload of a networkpacket of the transport layer protocol.

In one embodiment, the acceleration program 302 is designed, constructedor configured to work with appliance 205 to provide LAN sideacceleration or to provide acceleration techniques provided viaappliance 205. For example, in one embodiment of a NetScaler appliance205 manufactured by Citrix Systems, Inc., the acceleration program 302includes a NetScaler client. In some embodiments, the accelerationprogram 302 provides NetScaler acceleration techniques stand-alone in aremote device, such as in a branch office. In other embodiments, theacceleration program 302 works in conjunction with one or more NetScalerappliances 205. In one embodiment, the acceleration program 302 providesLAN-side or LAN based acceleration or optimization of network traffic.

In some embodiments, the network optimization engine 250 may bedesigned, constructed or configured to work with WAN optimizationappliance 200. In other embodiments, network optimization engine 250 maybe designed, constructed or configured to provide the WAN optimizationtechniques of appliance 200, with or without an appliance 200. Forexample, in one embodiment of a WANScaler appliance 200 manufactured byCitrix Systems, Inc. the network optimization engine 250 includes theWANscaler client. In some embodiments, the network optimization engine250 provides WANScaler acceleration techniques stand-alone in a remotelocation, such as a branch office. In other embodiments, the networkoptimization engine 250 works in conjunction with one or more WANScalerappliances 200.

In another embodiment, the network optimization engine 250 includes theacceleration program 302, or the function, operations and logic of theacceleration program 302. In some embodiments, the acceleration program302 includes the network optimization engine 250 or the function,operations and logic of the network optimization engine 250. In yetanother embodiment, the network optimization engine 250 is provided orinstalled as a separate program or set of executable instructions fromthe acceleration program 302. In other embodiments, the networkoptimization engine 250 and acceleration program 302 are included in thesame program or same set of executable instructions.

In some embodiments and still referring to FIG. 3, a first program 322may be used to install and/or execute the client agent 120, or anyportion thereof, automatically, silently, transparently, or otherwise.In one embodiment, the first program 322 is a plugin component, such anActiveX control or Java control or script that is loaded into andexecuted by an application. For example, the first program comprises anActiveX control loaded and run by a web browser application, such as inthe memory space or context of the application. In another embodiment,the first program 322 comprises a set of executable instructions loadedinto and run by the application, such as a browser. In one embodiment,the first program 322 is designed and constructed program to install theclient agent 120. In some embodiments, the first program 322 obtains,downloads, or receives the client agent 120 via the network from anothercomputing device. In another embodiment, the first program 322 is aninstaller program or a plug and play manager for installing programs,such as network drivers and the client agent 120, or any portionthereof, on the operating system of the client 102.

In some embodiments, each or any of the portions of the client agent120, a streaming client 306, a collection agent 304, SSL VPN agent 308,a network optimization engine 250, acceleration program 302, andinterceptor 350 may be installed, executed, configured or operated as aseparate application, program, process, service, task or set ofexecutable instructions. In other embodiments, each or any of theportions of the client agent 120 may be installed, executed, configuredor operated together as a single client agent 120.

D: Systems and Methods for Classifying Network Packets

Traditional QoS and acceleration processes may classify network packetsvia source or destination IP, but this may be inefficient andcounterproductive when a single IP address is associated with severalapplications. For example, a client at one IP address could execute aVoIP application requiring a high service priority, a web browsingprocess with medium priority, and an FTP client with a low priority, butif QoS and acceleration is only based on the IP address, thesedistinctions would be lost. Furthermore, even if port numbers are usedto attempt to distinguish services, distinctions between applicationsusing the same port are lost. For example, a system that considers alltraffic on TCP port 80 to be medium-priority web browsing may notrecognize that some of the traffic is a low-priority http file transfer,some is a medium or high-priority web application, and still other isstreamed multimedia using port 80 to tunnel through a firewall.

Further distinctions may exist, too. For example, in environments usingICA, RDP, or other application delivery protocols or systems,application data traffic for multiple applications, including wordprocessors, email applications, VoIP or video chat applications, filesystem explorers, or other applications, may be transmitted via a dataor control channel on a single port. Distinctions between theseapplications, and their differing requirements of QoS and priority wouldbe lost. Similarly, in environments in which application data frommultiple applications is sent via a single encrypted channel, anintermediary passing the encrypted traffic may not be able to determinepriority and implement proper queuing.

Accordingly, in some embodiments of the above discussed systems, networkperformance may be enhanced and optimized by providing QoS andacceleration engines with packet- or data-specific information. Inaddition to source and destination IP addresses and port numbers,packet- or data-specific information can include direction of traffic(client to host or server; server or host to client; or both), VirtualLAN (VLAN) ID, source or destination application or associatedapplication, service class, ICA priority, type of service,differentiated service code point (DSCP), or other information. Some orall of this information may be used to classify the network packet at aplurality of layers of a network stack, allowing for deep inspection ofthe packet and multiple levels of granularity of classification.

Referring now to FIG. 4A, shown is a block diagram of an embodiment of asystem for providing multi-level classification of a network packet. Inbrief overview, the system includes elements operating in kernel-mode302 and user-mode 303. Elements operating in kernel-mode 302 may includeone or more NICs, which may comprise one or more network interfaces 118,discussed above in connection with FIG. 1D; a plug-in framework 402, aQoS plug-in 404, and a client agent driver 406. These components mayinteract, communicate, or exchange data with elements operating inuser-mode 303 via a shared memory pool 408 and/or an IO control channel410. Elements operating in user-mode 303 may include a networkoptimization engine 250, an XML-Remote Procedure Call (RPC) client 426,a client agent control service, and storage of default policies 416 andconfiguration data 418. In some embodiments, network optimization engine250 may include a reporter 412, policy library 414, XML-RPC listener420, telnet listener 422, and a simple network management protocol(SNMP) agent 424. Furthermore, a management layer 428 providesmanagement components including a PHP: Hypertext Preprocessor (PHP)server; a command line interface (CLI), capable of providing a telnet orssh shell; an SNMP interface; and a management interface such asMicrosoft management console (MMC) and/or Windows managementinstrumentation (WMI) via a WMI provider service.

Still referring to FIG. 4A and in more depth, in some embodiments, thesystem may include a plug-in framework 402. Plug-in framework 402 maycomprise a library, service, process, module, extensible serviceprovider or other interface for managing or controlling the execution ofnetwork services. In some embodiments, plug-in framework 402 may providean interface between applications and layers of a network stack belowthe application layer. In some embodiments, plug-in framework 402 maymanage multiple plug-ins or network service providers and execute saidnetwork service providers or plug-ins in a proper order. For example, itmay be inefficient in some embodiments to encrypt data prior toperforming packet filtering operations. Such execution order may bedetermined dynamically, on a per-packet basis. For example, in oneembodiment, encryption may performed after content-filtering ontransmitted packets, and performed prior to content-filtering onreceived packets, such that content-filtering is always performed ondecrypted packets. Similarly, by determining which plug-ins are neededon a per-packet basis, plug-in framework 402 may reduce overhead forless used functions and increase efficiency of operations.

Plug-ins to the plug-in framework 402 may include encryption,compression, security, proxies, re-routing, filtering, deep-packetinspection, acceleration, flow control, disk-based or memory-basedcompression, or other services. In one embodiment, plug-ins may includea QoS plug-in 404. In some embodiments, QoS plug-in 404 may provideper-packet QoS and priority queuing, bandwidth limiting and regulation,and traffic blocking. In some embodiments, QoS plug-in 404 may set Typeof Service (ToS) bits in a packet for management by intelligent switchesand QoS-enabled routers. In a further embodiment, QoS plug-in 404 mayset ToS bits in conformance with a differentiated service code points(DSCP) scheme, such as that described in IETF RFC 2474, or any otherservice class and priority queuing system.

Plug-in framework 402 may, in some embodiments, include a packetinterception and filtering system. In one embodiment, plug-in framework402 may intercept a packet at one or more layers of a network stackbelow the application layer and utilize one or more filters on thepacket to determine one or more plug-ins to apply. For example, in oneembodiment, plug-in framework 402 may intercept a packet received by anetwork interface and may utilize a filter to determine if the packet isencrypted. If the packet is encrypted, plug-in framework 402 may apply adecryption plug-in. If the packet is not encrypted, plug-in framework402 may disable or not apply the decryption plug-in, reducing the amountof processing needed for the packet. In some embodiments, these filtersmay be applied on a per-packet basis. In another embodiment, thesefilters may be applied on a per-flow basis, a per-class basis, aper-link basis, or other less granular bases. In some embodiments,plug-in framework 402 may include and manage any components of anyembodiments of the client agent of FIG. 3.

As shown in FIG. 4A, plug-in framework 402 may provide plug-inmanagement for one or more NICs. Each NIC may provide one or morecommunications links or ports. These communications links may be definedto differentiate network traffic to different physical network segments,and may include multiple links per adapter. Filters may be applied byplug-in framework 402 to links according to a filter policy. A filterpolicy may indicate one or more filters to be applied to packetsreceived or transmitted via a link, and may include an order in whichthe filters are applied. Additionally, in some embodiments, multiplefilter policies may be applied to a link, and each policy may have anassociated priority. For example, in one embodiment, a first policy witha high order may be applied to all links, while a second policy with alower order may be applied to one or more specific links, such as linksassociated with internal network segments on a LAN. Plug-in framework402 may apply these policies based on the order, such that, in theexample above, the first policy may be applied first and the secondpolicy applied second. This allows for different filtering andprocessing operations on different network segments. In someembodiments, different policies may be applied to traffic on a link,depending on direction. For example, a first policy may be applied toinbound packets, while a second policy is applied to outbound packets.

In some embodiments, QoS plug-in 404 may comprise a service, process,subroutine, or other executable code for classifying packets andapplying QoS policies. In other embodiments, QoS plug-in 404 maycomprise a library, database, policy set, or functions executed byplug-in framework 402 for classifying packets and applying QoS policies.In one embodiment, QoS plug-in 404 provides functionality foridentifying various Ethernet protocols, including IP, non-IP, TCP andUDP traffic. In another embodiment, QoS plug-in 404 providesfunctionality for identifying traffic via stateful or deep packetinspection. Accordingly, QoS plug-in 404 may include a database orstorage element for recording or caching information about a packet,flow, link, and/or a state of a communication link. In one embodiment,QoS plug-in 404 may include a list of applications and functionality foridentifying whether a packet is associated with an application in thelist of applications. In some embodiments, the applications in theapplication list are pre-defined, either by a user or administrator of asystem, or by the manufacturer of QoS plug-in 404. In other embodiments,QoS plug-in 404 may dynamically recognize applications and add them tothe application list. In one embodiment, QoS plug-in 404 may attach orappend an application identifier to a packet after identifying anapplication associated with the packet. The application identifier maycomprise a code, name, string, pointer, table or list index, or otheridentifier to indicate an application in the application list associatedwith the packet.

In one embodiment, QoS plug-in 404 may provide one or more queues forbuffering network packets. In one embodiment, QoS plug-in 404 mayprovide a plurality of queues with each queue having an associatedpriority. For example, QoS plug-in 404 may provide a low priority queue,a medium priority queue, and a high priority queue and place packetsinto the queues responsive to QoS priorities associated with thepackets. QoS plug-in 404 may then process the queues in order ofpriority. For example, in one embodiment, QoS plug-in 404 may process ahigh priority queue at a faster rate, or more frequently, than theplug-in processes a low priority queue. In another embodiment, QoSplug-in 404 may move packets within a single queue. For example, QoSplug-in 404 may place high priority packets ahead of low prioritypackets within the queue. In one embodiment, packet priority may bedetermined responsive to ToS bits, DSCP bits, ICA priority tags, or anyother information in the packet. In some embodiments, the QoS plug-inmay have a plurality of queues corresponding to each of a number of oneor more priorities identified by the protocol, packet or otherwise, suchas a number of queues for the number of priorities identified by ToSbits, DSCP bits or ICA priority tags.

In some embodiments, QoS plug-in 404 may include one or more applicationclassifiers. An application classifier may comprise logic, executablecode, or other functionality for parsing a network packet received bythe QoS plug-in 404, either from an internal source or external source,at a network layer. In some embodiments, QoS plug-in 404 may include aplurality of application classifiers, each operating at a differentnetwork layer. Accordingly, the application classifiers may providemulti-level classification of network packets. In one embodiment, afirst application classifier, operating at a lower network layer, mayclassify a received packet as corresponding to a first application andattach an application identifier corresponding to the first application.The application classifier may pass the received packet to a secondclassifier, operating at a higher network layer, which may classify thereceived packet as corresponding to a second application. The secondclassifier, provided with both classifications via the applicationidentifier, may determine the second classification is more appropriate,and may modify the application identifier accordingly. This may be done,for example, to allow for queuing of encrypted network packets forprocessing by a decryption module. For example, a first classifier mayclassify an encrypted packet as a TCP packet or UDP packet, but due tothe encryption, may be unable to determine an application layer protocolof the packet. However, in some embodiments, a policy may indicate thatUDP packets should be decrypted at a higher priority than TCP packets.Accordingly, even though the first classifier may not have access to allof the information in the packet, information relevant to a processingorder of a decryption module may be identified, providing for additionalprioritized processing and QoS improvements. After decryption, thedecrypted packets may be passed to a second classifier to be furtheridentified and classified responsive to a higher layer protocol, stillachieving the fine-grained classification of high-levelapplication-based QoS.

Application classifiers may access a list of applications withassociated application identifiers. In some embodiments, theapplications in the list may be predetermined. In other embodiments,application classifiers may include functionality for recognizing a newapplication not in the list, and creating a new application identifier.For example, an application classifier may include a parser to identifyapplication data traffic associated with an application sent via aremote desktop protocol or ICA protocol. The application classifier maydetermine that the application does not have a corresponding applicationidentifier in the list of applications, and may create a new applicationidentifier in the list corresponding to the new application. Applicationidentifiers may include parameters of the application includingapplication name, type, protocol, service class, default policies, ToS,ports, URL, group membership, user, traffic flow, or other information.

Turning briefly to FIG. 5, illustrated is a block diagram of anembodiment of parent-child relationships of a plurality of layer 3-7protocols. One skilled in the art may readily appreciate that theparent-child relationships shown may be applied to other protocols,including Appletalk, ICMP, IPX, NetBIOS, SIP, DNS, NTP, POP, IMAP,Telnet, RDP, ICA, or any other type and form of networking protocols.Network packets may be associated with several protocols, which may beparsed along these parent-child relationships. For example, an HTTPnetwork packet is also a TCP and IP packet. In classifying packets, aQoS plug-in 404, network optimization engine 250, or other component mayclassify a packet at one layer and attach an application identifier. Insome embodiments, the application identifier may include a parentidentifier. Accordingly, an application classifier parsing a data packetto determine that the packet is, for example, an SAP packet, may attacha first application identifier that indicates the parent is HTTP. In anapplication identifier list, the protocol HTTP may be identified ashaving a parent protocol of TCP. Similarly, the protocol of TCP may beidentified as having a parent protocol of IP. Accordingly, a singlehigh-level application identifier may identify a plurality oflower-level protocols through these established parent-childrelationships. Additionally, groups may be created responsive to theserelationships. For example, TCP and UDP both have a parent relationshipwith IP, and thus may be grouped together as child protocols of IP.

In addition to grouping applications via parent-child relationships,applications may be identified as part of one or more predeterminedgroups. Predetermined groups may include, for example, web services,file delivery, directory services, VoIP, email, games, peer-to-peerapplications, client-server applications, routing protocols, securityprotocols, or other information. An application identifier may indicatethat the application is part of several groups via one or more flags.For example, an application identifier may include a plurality of flagsto indicate that an application is a web-based peer-to-peer multimediafile transfer utility using an IP protocol. In one embodiment, theapplication identifier may use a field with one or more bits set toindicate membership in the one or more groups. For example, in someembodiments, applications may be identified as belonging to one or moreof the following groups:

Group ID Definition Group Name 1 APP_GROUP_WEB Web 2APP_GROUP_EMAIL_COLLAB Email and Collaboration 4 APP_GROUP_CITRIX CitrixProtocols 8 APP_GROUP_DIRSVCS Directory Services 16APP_GROUP_CONTENT_DELIVERY Content Delivery 32 APP_GROUP_FILESERVER FileServer 64 APP_GROUP_GAMES Games 128 APP_GROUP_HOST_ACCESS Host Access256 APP_GROUP_VOIP Voice Over IP (VOIP) 512 APP_GROUP_LEGACY_NON_IPLegacy Or Non-IP 1024 APP_GROUP_MESSAGING Messaging 2048APP_GROUP_MULTIMEDIA Multimedia 4096 APP_GROUP_NETMGMT NetworkManagement 8192 APP_GROUP_P2P Peer-to-Peer (P2P) Applications 16384APP_GROUP_ROUTING Routing Protocols 32768 APP_GROUP_SECURITY SecurityProtocols 65536 APP_GROUP_SESSIONS Session 131072 APP_GROUP_SERVERSServers 262144 APP_GROUP_INFRASTRUCTURE APP_GROUP_INFRASTRUCTURE 524288APP_GROUP_MIDDLEWARE Middleware 1048576 APP_GROUP_GENERAL GeneralClassifiers 2097152 APP_GROUP_DB_ERP Database and Enterprise ResourcePlanning (ERP) Software 4194304 APP_GROUP_CLIENT_SERVER Client-Server8388608 APP_GROUP_IP IP Protocols

In some embodiments, application definitions may include: a uniqueidentifier to identify the application; an identifier of a parentapplication in the application list; a unique application name; a longname or description of the application; a composite group ID, asdiscussed above; a classifier identifier, such as a network, transport,session or application level classifier module used for classifyingtraffic; a next classifier identifier, for embodiments in which multipleclassifiers may be required to classify traffic; a flag to indicate ifthe application is capable of being accelerated; a flag to indicatewhether the definition has been modified; and a vector array ofapplication parameters. These application parameters may be defineddynamically. For example, in some embodiments, the vector array ofapplication parameters may include a name of a parameter, such as“port”; a type of parameter, such as “unsigned int” or “string”; a valueof the parameter, to be evaluated based on the type; minimum and maximumvalues of the parameter, if any; and a flag to indicate whether theparameter is user editable. Multiple parameters may be defined for anapplication.

Returning to FIG. 4A, client agent driver 406 may comprise a driver,library, API, service, or other interface for communication between aclient agent 120 or components of a client agent, discussed above inmore detail, and plug-in framework 402. In some embodiments, the clientagent driver comprises any embodiments of the client agent 120. Becausekernel-mode components and user-mode components may use differentstructures and objects, in one embodiment, client agent driver 406 maycomprise a translation library or API for allowing a networkoptimization engine 250 or components of the network optimization engineto communicate with plug-in framework 402 and/or QoS plug-in 404.

In some embodiments, kernel-mode components may interact, communicate,or exchange data with elements operating in user-mode 303 via a sharedmemory pool 408 and/or an IO control channel 410. In one embodiment,shared memory pool 408 may comprise a predetermined memory structure orlocation accessible by both kernel-mode components and user-modecomponents. In some embodiments, such memory structure or location mayinclude locking functionality, such as a semaphore, flag, or mutex, forpreventing components accessing the shared memory structure frominterfering. In one embodiment, an IO control channel 410 may comprise acommunications channel between various components of the system, such asa shared communications bus or virtual channel for system calls.

In some embodiments, such interaction, communication, or exchange ofdata via shared memory or IO control channel may include commands ormethods for:

Gathering information about a kernel level driver or specified networkadapter;

Mapping a specified memory region for communicated via shared memory;

Allocating memory or buffers for interaction;

Passing information about shared data structures from user-mode tokernel-mode;

Directing a kernel-mode driver to check for a number of packets to besent, and retrieving numbers of pending send and receive requests;

Retrieving counter information, names, or values;

Resetting one or more counters;

Setting or retrieving a debug level;

Enabling or disabling collection of information for packet tracing,including setting or retrieving an address mask for packet tracing;

Retrieving the contents of a buffer from the driver;

Enabling routing controls, including bypassing any traffic received fromthe input adapter, setting a virtual inline mode to either pass trafficto a network stack or return traffic to a sender, or discarding alltraffic;

Receiving NDIS WAN adapter addresses; and

Setting parameters for interframe delay, cache sizes, virtual memory, orany other parameters.

In some embodiments, reporter 412 may comprise a service, function,module, subroutine, logic, or other executable code for requesting andcollecting data, and creating reports or reporting objects. In someembodiments, reporter 412 may include an interface for requestinginformation from QoS plug-in 404, including statistics of droppedpackets and bytes, transmitted and received packets and bytes, latency,buffer size, and other information. In one embodiment, reporter 412 mayrequest such information at regular intervals, while in anotherembodiment, reporter 412 may request the information responsive to atrigger, such as a user request. In some embodiments, the interval maybe configured by a user or administrator.

In one embodiment, reporter 412 may collect data at a plurality ofdifferent levels or scopes. For example, in one such embodiment,reporter 412 may collect data specific to one or more QoS policies; oneor more applications; one or more service classes; one or more links; orsystem-wide data. Accordingly, this data may be provided in reportsfocused on each level or scope. In some embodiments, system-wide datamay include historical accelerated and un-accelerated data, allowing auser or administrator to determine the system efficiency gained throughacceleration. Because multiple links may be configured per networkadapter, and traffic received via one link may be transmitted tomultiple links, reporter 412 may collect data per link individually andaggregate the data to provide a complete overview of network traffic.Similarly, reporter 412 may collect application-specific data to providea user or administrator with an improved understanding of traffic flowto and from applications. For example, reporter 412 may collect anddisplay data sorted by application in order of: traffic sent; trafficreceived; packets sent; packets received; total traffic sent; totaltraffic; and total packets.

Likewise, in some embodiments, reporter 412 may collect and display dataassociated with a QoS policy, for each policy, on a per link basis. Inother embodiments, reporter 412 may collect and display data associatedwith one or more service classes, including rates of traffic, andstatistics by service class per link.

In some embodiments, historical data may be retained at varying levelsof granularity, including once per second, once per minute, once per 5minutes, once per hour, once per two hours, once per day, or any othervalue, and may be retained for varying durations, including one minute,one hour, one day, one week, and one month. In some embodiments,reporter 412 may retain multiple concurrent sets of historical data ofvarying duration and granularity.

In one embodiment, reporter 412 may create one or more reporting objectsresponsive to an acceleration or QoS policy. Objects may be createdspecific to one or more of traffic direction, object type, uniqueidentifiers of the policy, or parent objects. Reporter 412 may collect.For each object, in one embodiment, reporter 412 may collect statisticsor data including a number of bytes or packets processed by the policy,a number of discarded bytes or packets, and a number of dropped bytes orpackets. Such packets or bytes may be dropped or discarded due toblocking or regulation policies.

Reporter 412 may include one or more APIs or XML-RPC methods, which, insome embodiments, may be applied to various reporting objects,statistics, or collected data discussed above, such as: getting a sortedlist of applications in order of statistics or counters for the object,such as a list of dropped packets per application; getting a sorted listof all applications in a specified group in order of statistics orcounters for the object, such as all HTTP applications, or allapplications associated with Google; getting report data for a specificlink; getting report data for a specific service class; or gettingreport data for a specific QoS policy. Such reports, in one embodiment,may be output as an XML file or array of link name and counter statisticpairs. Furthermore, for managing reports and counters, reporter 412 mayinclude XML-RPC methods for resetting one or more application counters,link counters, service class counters, or QoS policy counters.

Because a lot of data may be stored in extended performance counters,which some reporting objects may not use, in some embodiments, reporter412 uses selective data collection and reporting. In these embodiments,each reporting object may include one or more flags for relevant data,such as bytes, packets, bytes discarded, packets discarded, bytesdropped, packets dropped, and may collect and report only flagged data.In another embodiment, the reporting object may include a flagindicating to collect and report all data.

In some embodiments, reporter 412 may include or manage counters fortransmitted dropped packets; received dropped packets; NIC stops;receive buffer drops; outbound packets filtered by a copy or clonesetting; traced packets or packets not included in a trace; receivedpackets; packets dropped from a queue; filters that cannot be allocatedin memory; NIC no carrier indicators; timeout indicators; stops ortimeouts; packets received, dropped, or received with padding while in aloopback mode; received or transmitted packets, bytes, errors, droppedpackets; multicast packets received or transmitted; collisions detected;receive length errors; receive oversize errors; receive CRC errors;receive frame errors; receive buffer FIFO errors; receive buffer missedpacket errors; transmission aborted errors; transmission carrier losserrors; transmission buffer FIFO errors; transmission heartbeat errors;transmission window errors; or number of compressed packets or bytestransmitted or received.

In other embodiments, reporter 412 may include or manage countersassociated with a plug-in framework for a number of bytes or packetsreceived from a network stack; a number of bytes or packets receivedfrom the stack and passed to a filter; a number of bytes in IPSecpackets or number of IPSec packets received from the stack; a number ofbytes or packets received from network adapters; a number of bytes orpackets received from adapters and passed to a filter; a number of bytesin IPSec packets or number of IPSec packets received from adapters; anumber of packets dropped; a number of packets received, passed to afilter, and/or dropped by protocol; a number of trace packets dropped; anumber of packets lost; a number of packets dropped from a transmissionqueue; a number of times a packet could not be removed from atransmission queue or was dropped due to stalls; adapter connects,disconnects, or failures; or number of times that an adapter went up,down, or into standby.

In some embodiments, counters may be specific to an adapter, or on aper-adapter basis, and may include packets received or transmitted;bytes received or transmitted; packets or bytes dropped from atransmission queue; and packets or bytes dropped from a receive buffer.

Similarly, to enhance the usability of reports, reporter 412 may apply afilter to data prior to generating reports. In some embodiments,reporter 412 may filter relevant data based on counters, such as bytes,packets, bytes discarded, packets discarded, bytes dropped, packetsdropped, or all data. In other embodiments, reporter 412 may filterrelevant data based on time, such as data collected within the lastminute, last hour, last day, last week, last month, or all data. Instill other embodiments, reporter 412 may filter relevant data based onflow or traffic direction, including inbound, outbound, or both. In yetstill other embodiments, data may be collected as both a counter valueand a rate of change, and reporter 412 may filter data by type,including value, rate, or all. In other embodiments, reporter 412 mayfilter data by reporting only a specified number of active objects, suchas the top ten most active applications, the top five links dropping themost inbound packets, or any other number of objects. In still otherembodiments, reporter 412 may filter data by application group, such asall applications belonging to the group “games”. In yet still otherembodiments, reporter 412 may filter data by link, such that reporter412 may report only statistics for a specific link. In many embodiments,multiple filters may be applied. For example, in one such embodiment,reporter 412 may report the rate of dropped bytes per second of inbounddata for an email application over the past hour for link #3. Reporter412 may, in some embodiments, sort the data prior to reporting.

Policy library 414 may comprise a library, database, registry, datafile, or other data storage element for storing, modifying, andretrieving one or more policies for use by network optimization engine250 and/or QoS plug-in 404. In one embodiment, policy library 414 mayinclude default parameters, which may be stored in a default policy file416. These policies may be applied by network optimization engine 250and/or QoS policy 404 to packets, flows, or links. In one embodiment,management functions, discussed in more detail below may be treated asservices accessed via an internal or virtual link. In these embodiments,to avoid processing packets directed to these functions withcompression, encryption, QoS, or other acceleration features, policylibrary 414 may apply a policy to each of one or more external ornon-management links, indicating that traffic on each of the one or moreexternal or non-management links should be sent to an acceleratorfunction. Similar policies may be used for various types of traffic,including address resolution protocol traffic, generic routingencapsulation traffic with non-internal destinations, or other types oftraffic that should not be processed by one or more accelerationfeatures of network optimization engine 250.

In one embodiment, a QoS policy may include one more actions to beapplied when traffic matches one or more filter conditions of thepolicy. In one embodiment, an action to be applied may includeregulating or limiting the bandwidth of the traffic matching the filtercondition. In a further embodiment, an action may include regulating orlimiting the bandwidth of the traffic at different levels, depending ondirection of flow. For example, a policy may indicate to limit inboundtraffic to a first rate, and limit outbound traffic to a second rate. Inanother embodiment, an action to be applied may be to process trafficmatching the filter condition at a minimum latency, or as fast aspossible, which may include prioritizing the minimum latency trafficahead of other traffic, or buffering or delaying other non-minimumlatency traffic. In another embodiment, an action to be applied may beto block traffic matching the one or more filter conditions.

In yet another embodiment, an action to be applied may be to process thetraffic according to a priority level. In some embodiments, multiplepriority levels may exist including three (high, medium, low); five(high, high-medium, medium, low-medium, low); seven (very-high, high,high-medium, medium, low-medium, low, very low); or any other number. Inone embodiment, numerical priority values may be used for each level.For example, in one embodiment, priority levels of 10, 20, 30, 40, 50,60, and 70 may correspond to the seven priority levels discussed above.However, other values may be used, providing coarser or finer divisionsas necessary. In some embodiments, a priority level of medium may beused when there is no priority specified in a policy. In someembodiments, priority levels may exist for background traffic.Processing the traffic according to the priority level may, in someembodiments, comprise processing traffic at varying rates or frequenciesaccording to priority, or performing other acceleration functions,described herein.

In still another embodiment, an action to be applied may be to mark anetwork traffic packet matching the one or more conditions with ToS bitsfor management by intelligent switches and QoS-enabled routers. Inanother embodiment, the action may be to mark the packet with DSCP bits.In yet still another embodiment, the action may be to mark the packetwith an ICA priority tag.

As discussed above, policies may be applied to packets that match one ormore filter conditions. In some embodiments, these filter conditions mayinclude an application name, type or identifier, a port, a direction offlow, a local IP address, a remote IP address, a VLAN ID, a DSCPsetting, a priority, a packet size, a Web Cache Communication Protocol(WCCP) service group ID, or any other type of information. Filterconditions may include an order of precedence of application, such thatone condition with a high precedence may be applied before a conditionwith a low precedence. In some embodiments, a user or administrator of asystem may adjust the precedence of one or more filter conditions.

Referring briefly ahead to FIG. 4B, illustrated is a block diagram of anembodiment of a network optimization engine for providing multi-levelclassification of a network packet. Policy library 414 may provide fortranslation or conversion from data structures useable by QoS plug-in404 to those useable by network optimization engine 250 or otheruser-mode components. In some embodiments, such translation orconversion may be provided via one or more classifiers, configurationpolicy translators, and report translators. Classifiers may be used byQoS plug-in 404 or network optimization engine 250 to define andclassify applications. Classifiers may be updated by policy library 414responsive to changes in definitions of applications. Similarly,configuration policy translators may be created responsive to linkpolicies, service class policies, and/or QoS policies. For example,rules in a service class filter and actions in a QoS policy may be usedto build a policy, which may be passed to QoS plug-in 404 using thetranslator. Similarly, data for reports, discussed in more detail above,may be collected or processed using a translator provided by policylibrary 414.

In some embodiments, discussed in more detail below, a classifier maycomprise an application, program, module, service, daemon, subroutine,logic, functionality, or other executable code for classifying a packetas corresponding to an application. In one embodiment, a classifier mayinclude a parser for detecting or locating information in a packetidentifying the packet as corresponding to the application. In anotherembodiment, a classifier may include or manage an application list withone or more applications and one or more corresponding applicationidentifiers. In a further embodiment, discussed in more detail below,the application list may include information of a parent-childrelationship with another application. In another further embodiment,discussed in more detail below, the application list may include groupmembership information of an application. In some embodiments, theclassifier may include functionality for parsing a packet forinformation identifying a new application not in the application list,and adding the new application to the application list and establishinga new application identifier for the new application.

In some embodiments, for QoS and acceleration to work together, link andservice class policies need to be set up in a policy tree. In oneembodiment of such a tree, two link policy objects may be created foreach link, one for each direction (inbound and outbound). Service classpolicies may be created under each link policy. Thus, when a packetarrives, the packet may be classified, statistics may be gathered forreporting, and QoS or acceleration actions may be applied.

Returning to FIG. 4A, in some embodiments, network optimization enginemay include an XML-RPC listener 420, a telnet listener 422 and/or anSNMP agent 424. XML-RPC listener 420, telnet listener 422, and SNMPagent 424 may comprise one or more services, functions, subroutines,daemons, applications, or other executable code for monitoringcommunications between network optimization engine 250, managementfunctions 428, and configuration storage 418. For example, SNMP agent424 may provide processing and transmission of SNMP management data andcommands, either internally or via a network connection. XML-RPClistener 420 may interface with an XML-RPC client 426 which may, in someembodiments, comprise a web browser, a shell, terminal or any other typeand form of client interfaces for processing XML-RPC calls or otherHTTP, PHP, or similar traffic. In one embodiment, XML-RPC client 426 mayinterface to a WMI provider or other management interface for automationand monitoring.

In some embodiments, network optimization engine 250, QoS plug-in 404and/or client agent driver 406 may include or communicate with a licensemodule. In one embodiment, if the license module detects that theproduct is not licensed, one or more filter or QoS policies may bedisabled, such that network traffic is unprocessed.

Deployment Examples and Service Class and Policy Definitions

The system shown in FIG. 4A may be deployed in various embodiments,including as part of an intermediary device such as a router, networkswitch, firewall, network bridge, or other device, or as part of aclient or a server. In these various embodiments, network ports of thesystem may be used together for bridging or routing from one networksegment to another, or may be used separately. In these embodiments, thesystem may communicate with other routers via normal routing,policy-based routing, web cache communication protocol (WCCP) routing,or any other routing mechanism. For example, the system may be deployedin a direct or end-point mode, an in-line or virtual in-line (VI) mode,a routed mode, a WCCP mode, a proxy mode, a tunnel mode, or in any otherdeployment mode.

In these embodiments, NIC ports or adapters may use multiple links, asdiscussed above. Each link may be identified by one or moreconfiguration parameters. These parameters may include a link ID, whichmay be an internal index or unique ID; an adapter name, which may bedefined by a user or administrator or generated automatically; a linktype identifier, which may be used to define a link object type, such asLAN, WAN, site, or any other type; one or more filter rules to beapplied to the link; maximum inbound link speed or bandwidth in bps orany other metric; maximum outbound link speed or bandwidth in bps or anyother metric; and an order in which policies or communicationsassociated with the link are processed, such that higher order policiesmay be processed before lower order policies. In some embodiments, theparameters may be modifiable by a user or administrator of the system,and the parameters may include a modified flag set to, a zero value insome embodiments, or a non-zero value in other embodiments, to indicatethe policy has been modified.

To support QoS in different network topologies, configurations anddeployment modes as discussed above, each link definition oridentification may further include one or more filtering parameters,including one or more IP addresses, adapter names, Ethernet addresses,VLAN IDs, WCCP service group IDs, or any other identifier. In someembodiments, each link may include a single entry for IP addressesand/or Ethernet addresses, such that there is no differentiation betweensource and destination addresses. In one such embodiment, the addressesmay be used as source or destination addresses based on the direction ofa link policy—i.e. inbound or outbound. For example, a link with anaddress of 1.2.3.4 may have a filter policy for inbound traffic that isapplied to traffic with a destination IP of 1.2.3.4, and a filter policyfor outbound traffic that is applied to traffic with a source IP of1.2.3.4. In some embodiments, IP addresses may be specified or definedin different formats, including dotted strings, arrays of bytes, and/orinteger values.

In one embodiment, links may be managed through one or more remoteprocedure call commands or methods, as discussed above. These methodsmay include commands for creating a link, renaming a link, deleting alink, changing a link, getting parameters of a link, resetting one ormore counters associated with a link, or getting statistics or countervalues from the one or more counters associated with the link. Furthercommands may be associated with the methods for use in a CLI or otherinterface, including commands for displaying link statistics in one ormore formats, such as XML; displaying or dumping characteristics of alink in one or more formats, such as XML; displaying or dumping cachedcharacteristics of a link in one or more formats, such as XML;displaying a list of current links or applications utilizing links; andresetting one or more counters associated with a link. In oneembodiment, link definitions may be stored in a parameter file in aformat, such as XML. These definitions may, in some embodiments, befirst created during initialization. The hierarchy afforded by XML maybe used, for example, to denote policies or service classes associatedwith links in both inbound and outbound modes:

Link—1 (Inbound)

-   -   Service Class—1    -   Service Class—2    -   Service Class—n

Link—1 (Outbound)

-   -   Service Class—1    -   Service Class—2    -   Service Class—n

Link—2 (Inbound)

-   -   Service Class—1    -   Service Class—2    -   Service Class—n

Link—2 (Outbound)

-   -   Service Class—1    -   Service Class—2    -   Service Class—n

Service classes, in some embodiments, may be used to differentiatebetween priorities of traffic. As discussed above, DSCP bits may be usedto denote service classes, with each class being a group of DSCPs withthe same precedence value. Values within a class may offer similarnetwork services, but with slight differences (such as “gold”, “silver”and “bronze” performance sub-classes). As discussed above, IETF RFC 2474describes some service classes via code numbers. In some embodiments,DSCP bits may be mapped to some or all of these code numbers to ensurecompatibility with RFC 2474-compliant switches, as shown below:

RFC 2474 Class DSCP Class Class Code Precedence Value Best Effort BestEfforts 0 0 0 Class 1 8 Class 1 - Gold AF11 10 1 40 Class 1 - SilverAF12 12 48 Class 1 - Bronze AF13 14 56 Class 2 16 2 64 Class 2 - GoldAF21 18 72 Class 2 - Silver AF22 20 80 Class 2 - Bronze AF23 22 88 Class3 24 3 96 Class 3 - Gold AF31 26 104 Class 3 - Silver AF32 28 108 Class3 - Bronze AF33 30 120 Class 4 32 4 128 Class 4 - Gold AF41 34 136 Class4 - Silver AF42 36 144 Class 4 - Bronze AF43 38 152 Express Express 40 5160 Forwarding Forwarding Expedited Expedited 46 184 Forwarding Discard4 Control Internetwork 48 6 192 Control Control Network Control 56 7 224

Similarly, other priority codes may be mapped to one or more serviceclasses. For example, in some embodiments, ICA priority tags may includethe values 0-3, representing high, medium, low, and background tasks,which may be mapped to one or more DSCP bits or other service classlevels.

In some embodiments, QoS policies may include multiple parametersincluding: a unique identifier to identify a policy action; one or moreaction flags to identify which actions are used with the QoS policy,such as blocking, providing bandwidth limiting or regulation, providingtraffic with minimum latency, etc., as discussed above; a unique QoSpolicy name; a priority level; a service bits setting to change ToS orDSCP bits of a packet processed according to the policy; a maximum inputand/or output bandwidth; an ICA priority value or other protocolpriority value to include with the packet; and a flag indicating whetherthe policy has been modified.

In some embodiments, different actions such as acceleration, QoS,reporting and classification may be applied to packets based on serviceclass. In one embodiment, reporting and classification actions may beimplicit, or may be required for all service classes. Thus, in thisembodiment, only two options—QoS and acceleration—may be reported to auser or administrator or provided as configuration options. In someembodiments, acceleration actions may be based on the applicationsincluded in a service class definition. For example, a service class mayonly be accelerate-able if it includes applications capable of beingaccelerated. Not all service classes are relevant for acceleration,depending on the application or applications used to define a serviceclass. Some dynamic protocol applications can't be configured foracceleration. Thus, options may be provided in a configuration tool fora user or administrator to select acceleration and/or QoS tasks to beutilized for a class. In some embodiments, some statistical parameterssuch as compression ratio or accelerated vs. un-accelerated traffic willnot be available for classes not selected for acceleration usage. In oneembodiment, when an option for acceleration usage is selected, theconfiguration tool may only display the list of applications which canbe accelerated. In some embodiments, the configuration tool may includea mechanism to find which applications can be accelerated.

In some embodiments, service classes may include or be defined byparameters, such as a unique identifier for the service class; aprecedence order for processing of the policy related to the serviceclass; one or more flags of supported policies; one or more filter rulesin an ordered list; one or more QoS policies, which, in one embodiment,may comprise an array of values of policy identifier and link identifierpairs; one or more acceleration policies; a flag identifying if theservice class has been modified; and a flag that may be set to enable ordisable the service class, without deleting the parameters from thedevice configuration. In some embodiments, acceleration policies mayinclude flow control, disk based compression, and memory basedcompression. QoS policies may be separately defined within a serviceclass parameter, and may be associated with multiple service classes.

In some embodiments, XML-RPC commands and methods may be used to manageservice classes. These commands and methods may include commands for:creating a service class; renaming a service class; deleting a serviceclass; changing a service class parameter or parameters; getting orretrieving a service class parameter or parameters; resetting one ormore counters associated with the service class; getting or retrievingone or more counter values or statistics associated with the serviceclass; setting an acceleration policy or policies for the service class;setting a QoS policy or policies for the service class; updating anorder of precedence of the service class; and changing an enabled ordisabled state of the service class. Commands for a CLI or otherinterface may include commands to display a list of current serviceclasses; display entries in an index table of service classes; displayservice class statistics, in one or more formats, such as XML; convertor output a service class definition in XML; retrieve a cached XMLdefinition of a service class; reset a service class driver; reverse aservice class index, to control order of application; dump connectioninformation of connections associated with a service class; and resetone or more service class counters. In one embodiment, the service classlist may be stored in an XML file, and may be created as a default listduring initialization. In some embodiments, default service classes maybe hard coded, while in others, they may be generated responsive topresence of one or more applications or components duringinitialization.

In some embodiments, a system such as that shown in FIG. 4A may comprisefunctionality for disabling one or more features. This may be helpful,particularly for testing purposes. In some embodiments, one or moreacceleration policies and/or one or more QoS policies may be disabled,without deleting them from an active configuration. In one embodiment,disabling policies may be controlled a system state parameter, such thatQoS policies and/or acceleration policies may be enabled or disabledbased on the setting or unsetting of a predetermined bit, such as afirst bit for QoS policies and a second bit for acceleration policies.In a further embodiment, an XML-RPC method may be used to get a currentstate of system features, such as QoS or acceleration being enabled ordisabled; or used to set a current state by changing the value of thepredetermined bit or bits.

In some embodiments, the system may include functionality for processingencrypted traffic. For example, in one embodiment, the system maydecrypt, compress, and re-encrypt SSL traffic. Service classes may beutilized with SSL traffic by filtering SSL traffic based on one or morecharacteristics, such as destination port, SSL server address, andsource IP address. As discussed above in connection with FIG. 4A, asystem including a reporter 412 may collect and report statisticsassociated with SSL traffic. To provide per-application levelstatistics, in some embodiments, the reporter may use a multi-levelclassification method to classify SSL traffic as associated with orcorresponding to an application. Per-application statistics may then becollected and reported for the encrypted traffic, along with statisticsfor unencrypted traffic. For example, in one such embodiment, a serviceclass may be defined for messaging API (MAPI) traffic, with a filter ofan SSL server IP and port address, and traffic associated with that IPand port may be classified as MAPI traffic. If another service classincludes a MAPI-enabled application, such as Microsoft Outlook, theencrypted traffic may be reported along with unencrypted trafficassociated with the MAPI-enabled application. Conversely, if no serviceclasses include MAPI-enabled applications, then in some embodiments, theencrypted traffic may be reported as unclassified TCP traffic.Accordingly, it may be preferable to configure an application-specificservice class along with the SSL service class.

In some embodiments, a system may include a default configuration withdefault link and service classes that a user or administrator may beprevented from deleting. For instance, default link and service classesmay be used, in some embodiments, as templates for constructing newlinks and service classes, and accordingly should not be deleted. Inthese embodiments, service classes, links, policies and/or other objectsmay include one or more flags or predetermined bits set to indicate oneor more of: the user is not allowed to delete the object; the user isnot allowed to edit the object definition; the user is not allowed tochange the order of the object; the user is not allowed to change theQoS policy and/or actions for the object; and the user is not allowed tochange the acceleration policy for the object. Each flag may berepresented by an independent bit in a string, such that multiple flagsmay be independently set.

In some embodiments, other defaults may be utilized, too. For example,the system may include default maximum queue depths for packet queuing,and maximum number of entries and/or table size values for reportingapplication, link, service class, or other statistics. In someembodiments, the system may also include preconfigured filter rules,such as a rule to send all TCP traffic to the QoS plug-in and/or networkoptimization engine 250 for classification and/or further processing.This may be done, for example, to avoid additional processing ofmanagement interface traffic. In other embodiments, the system mayinclude a rule to direct generic routing encapsulation (GRE) tunneledtraffic to the QoS plug-in. For example, one rule may indicate that allGRE traffic, whether TCP or UDP, that is not web cache communicationprotocol traffic may be passed to the QoS plug-in or networkoptimization engine for classification or further processing. Anotherrule with a higher precedence may also be used to intercept GRE WCCPtraffic. In one embodiment, such a rule may be applied only to incomingtraffic directed to a hosted IP address.

In one embodiment, internal address resolution protocol (ARP) or“pseudo-ARP” messages may be utilized to identify the proper adapter touse for specified traffic. In such embodiments, the system may include apreconfigured rule to intercept outbound TCP synchronization (SYN)packets on a predetermined port, such as 5555, for passing to a QoSplug-in or network optimization engine. Once the packet is passed to oneof these modules, the module may use MAC information in the packet toidentify an adapter and update an ARP table. To ensure that the SYNpacket does not result in a hanging connection, the module may replywith an RST packet back to the original socket to terminate theconnection.

Other preconfigured policies that may exist in some embodiments includean exclude policy, in which specified traffic is dropped. In oneembodiment of a system with such a policy, traffic matching a filter setmay have a policy applied, with the policy lacking any action thatcauses the traffic to be sent to a QoS plug-in or network optimizationengine. Accordingly, by placing this policy first in precedence, thetraffic may be excluded from further processing. Filters that may beused, in some embodiments, include predetermined port numbers, such as3389 for RDP terminal services; 80 or 443 for HTTP communications; 22for SSH; 23 for telnet; or other ports, including those used forinternal XML-RPC protocol messages. In other embodiments, the filtersmay include source or destination IP addresses matching hosted IPaddresses of the system, such as loopback addresses or internalconfiguration addresses. In still other embodiments, in which the systemuses virtual IP (VIP) addresses, filters may be used to exclude TCPtraffic with source or destination IP addresses matching virtual IPaddresses. In yet still other embodiments, in which the system interactswith another system to provide high availability (HA) services, filtersmay be used to exclude HA management traffic with source or destinationIP addresses matching IP addresses hosted on an HA management adapter.

In some embodiments, for managing signaling channel traffic between aclient and appliance or applications on the system, the system mayinclude a preconfigured signal channel policy. In one such embodiment,outbound traffic from a signaling channel IP and port may be redirectedback and inbound traffic to the signaling channel IP and port may bedirected to a QoS plug-in or network optimization engine.

In some embodiments, the system may include a preconfigured policy toapply QoS to UDP traffic without performing acceleration techniques onthe traffic. For example, in systems that serve as a proxy for UDPtraffic from a WCCP router, MAC and IP addresses may be flipped to allowcontent routing for real-time redirection of traffic flows. Accordingly,in one embodiment, the system may include a filter that intercepts UDPtraffic with destination MAC addresses matching a system interface anddestination IP address not matching an interface, and passes the trafficto a QoS plug-in for prioritization.

In some embodiments, the system may include bandwidth managementfunctionality. In an embodiment of aggressive bandwidth management, thesystem may ignore conventional congestion-control and packing signals.For example, the system may resend packets in response to packet loss,but not reduce transmission rates; and/or may not use a slow-startprotocol, but immediately send packets at the negotiated bandwidth. Insome embodiments, the system may ignore self-clocking routines. Forexample, in one such embodiment, the system may send data to fill awindow, such as an 8 MB window, regardless of not receiving any ACKpackets. In these aggressive bandwidth management embodiments, areceiver-side QoS system may not be able to slow down a remote senderutilizing these aggressive techniques, without adjusting negotiatedbandwidth through TCP options.

Group ID Definition Group Name 1 APP_GROUP_WEB Web 2APP_GROUP_EMAIL_COLLAB Email and Collaboration 4 APP_GROUP_CITRIX CitrixProtocols 8 APP_GROUP_DIRSVCS Directory Services 16APP_GROUP_CONTENT_DELIVERY Content Delivery 32 APP_GROUP_FILESERVER FileServer 64 APP_GROUP_GAMES Games 128 APP_GROUP_HOST_ACCESS Host Access256 APP_GROUP_VOIP Voice Over IP (VOIP) 512 APP_GROUP_LEGACY_NON_IPLegacy Or Non-IP 1024 APP_GROUP_MESSAGING Messaging 2048APP_GROUP_MULTIMEDIA Multimedia 4096 APP_GROUP_NETMGMT NetworkManagement 8192 APP_GROUP_P2P Peer-to-Peer (P2P) Applications 16384APP_GROUP_ROUTING Routing Protocols 32768 APP_GROUP_SECURITY SecurityProtocols 65536 APP_GROUP_SESSIONS Session 131072 APP_GROUP_SERVERSServers 262144 APP_GROUP_INFRASTRUCTURE APP_GROUP_INFRASTRUCTURE 524288APP_GROUP_MIDDLEWARE Middleware 1048576 APP_GROUP_GENERAL GeneralClassifiers 2097152 APP_GROUP_DB_ERP Database and Enterprise ResourcePlanning (ERP) Software 4194304 APP_GROUP_CLIENT_SERVER Client-Server8388608 APP_GROUP_IP IP ProtocolsE: Prioritizing Highly Compressed Traffic and Traffic Assigned to aParticular Traffic Class

As discussed above, in some instances the network optimization enginecan be used to classify network packets according to one or many networkclasses. In particular, the network optimization engine can be used toclassify traffic according to one or more characteristics. For example,the network optimization engine can be used to transmit data packetsbelonging to a particular network traffic class according to a differentQoS than the QoS applied to other data packets. Allowing the networkoptimization engine to differentiate data packets according to multipleclasses of service shapes network traffic thereby allowing resourcesharing among applications and services that otherwise use differentnetwork services but that belong to the same administrative class.Selectively applying network traffic classes to similar resources can beaccomplished when application data traffic is transmitted fromsubstantially the same output link. This output link can be a commonrouter, switch or other appliance and is commonly referred to as awide-area-network pipe (“WAN pipe”).

Illustrated in FIG. 6 is one embodiment of a system that utilizes WANpipes to shape traffic and thereby ensure link sharing among integratedservices. A common link 650 facilitates the transmission of networktraffic generated by back-end servers 660. The corresponding datatransmission from the common link 650 over the network 670 can bereferred to as a WAN pipe 620. The network 670 can be any networkdescribed herein. An appliance 610 situated between the common link 650and a WAN can classify and declassify data packets using a networkoptimization engine 250. Upon classifying or declassifying the datapackets, the appliance 610 can transmit the data packets over a network680 to a client machine 630 executing a network optimization engineclient 250′. The network 680 can be any network described herein.

The back-end servers 660 can be any computer described herein and insome instances can be any server 106 described herein. In some instancesthe servers 106 can be a server farm or any collection of serversgenerating and transmitting data over the network 670 in data packets.Applications executing on the servers 660 can require different networkservices thereby causing data packets containing data generated by anapplication to be classified according to the required network services.For example, a peer-to-peer application may belong to a differentapplication group than a VoIP application. Data packets comprising datagenerated by a peer-to-peer application may therefore be classified witha network traffic class or QoS that indicates the network servicesrequired to efficiently and best transmit the peer-to-peer applicationnetwork traffic. The network traffic class and QoS for the VoIPapplication, however, may be different from that of the peer-to-peerapplication, and can reflect the network services required toefficiently transmit the VoIP application network traffic.

Typical network configurations include a common link 650 or appliancethat can be used to facilitate the transmission of data from a pluralityof sources over a network 670. In one instance, the common link 650 canbe a single router, firewall, switch or network management server. Thesecommon links 650 can be physical computing devices that are physicallyor wirelessly connected to the one or more back-end servers 660. Virtualcommon links 650, in some embodiments, can be virtual machines executingon a computer or appliance. Within these virtual machines,virtualization applications can execute to perform the functionality ofa physical router, firewall, switch or network. In other instances, thecommon link 650 can be a cluster of appliances, physical or virtualcomputing devices that operate together as a single common link 650. Thecommon link 650 can also be referred to as a common output link.

Network traffic handled and transmitted by the common link 650 can bereferred to as a WAN pipe 620. The common origin of traffic transmittedover a WAN pipe 620 can advantageously provide opportunities to leveragethe shared link of integrated services and can permit resource sharingamongst applications. For example, network traffic, and in particularenterprise network traffic, can contain multiple network service classessuch as real-time service, best effort service and others. As mentionedearlier, packets from different sessions or applications that belong todifferent network service classes (i.e. they require different networkservices) can better interact with one another when they share a commonoutput link 650 (i.e. a WAN pipe 620). Scheduling algorithms executed bythe output link 650 and other appliances downstream from the output link650 can be used to take advantage of the WAN pipe 620 to provide: linksharing between different applications executing on the back-end servers660; real-time traffic management of traffic transmitted over the WANpipe 620; and best-effort traffic management of traffic transmitted overthe WAN pipe 620. Each of these network traffic optimization techniquescan be managed by a common mechanism. In some instances this commonmechanism or structure can execute on the common link 650 or on adownstream device.

One example of how the common link 650 or downstream device can providereal-time traffic management includes using a leaky bucket algorithm tomanage network traffic. This algorithm can be used to manage sessions byensuring that bursty traffic conditions conform to predefined networktraffic flow limits. An example of how the common link 650 or downstreamdevice can provide a best-effort traffic management of network traffictransmitted over the WAN pipe 620 includes accurately estimating anamount of available bandwidth and fairly distributing bandwidth amongstsessions.

In some embodiments, the common link 650 or downstream device can use aHierarchical worst case fair weighted queuing (HWF2Q+) protocol tofairly distribute traffic. This protocol, in some embodiments, can beoptimized to ensure real-time, best-effort traffic management bycreating levels of priority within delay-sensitive traffic and fairnessamong flows within those priorities. For example, if there are twodelay-sensitive flows (e.g. two VoIP streams) associated with a QoS thatguarantees a minimum latency, the protocol can prioritize the streams byfairly distributing bandwidth amongst both streams, or prioritizing onestream over another (e.g. give priority to corporate VoIP over Skype™).In some embodiments, the protocol can provide bandwidth limits and QoSguarantees predicated on an adaptive priority adjustment. Thisadjustment can be sensitive to the number of network streams.

The modified HWF2Q+ algorithm described above can provide benefits notenjoyed by traditional quality of service algorithms. Typical QoSalgorithms often violate link sharing goals while attempting to providetight delay bounds for real-time service. Links are often overloaded bythese typical algorithms when real-time session traffic begins totransmit over the network. This often causes and increase in theworst-case delay and non-real-time sessions can experience great delay.The strong worst-case fairness properties of the above describedmodified HWF2Q+ algorithm provide tight delay bounds while not violatinglink sharing goals.

Determining whether an appliance or device truly provides fairdistribution of bandwidth can include using protocols or methods toanalyze the delay and bandwidth distribution fairness of a packet fairqueuing (PFQ) server. In particular, determining whether a PFQ serverfairly distributes bandwidth resources includes determining whether thePFQ server requires all PFQ protocols to have the least amount of delay,whether the PFQ server has the smallest worst-case fair index (WFI)among all PFQ protocols, and whether the PFQ server has a relatively lowimplementation complexity. These tests can be used to determine whethera common link 650 or downstream device best takes advantage of a WANpipe 620 to provide best-effort and real-time traffic management.

While traffic may be optimized on a common link 650, in some instancesthe traffic can be optimized by a network optimization engine 250executing on a downstream appliance or computing device 610. Thedownstream appliance or computing device 610 can be any computer orappliance described herein. In particular, the downstream appliance 610can be a NetScaler, WANscaler or Branch Repeater manufactured by CitrixSystems. The network optimization engine 250 is the network optimizationengine described above in FIGS. 2A, 2B, 4A and 4B. In some embodimentsthe network optimization engine 250 can be referred to as a trafficshaping engine or a traffic optimization engine 250. In otherembodiments, the network optimization engine 250 can be a moduleexecuting within the network optimization engine 250.

The network optimization engine 250 can be used to take advantage ofnetwork traffic originating from a common source, i.e. network traffictransmitted over a WAN pipe 620, by applying various QoS algorithms andtraffic shaping protocols to the network traffic. By applyingoptimization algorithms and protocols to the network traffic, thenetwork optimization engine 250 can optimize the method in which networktraffic is transmitted from the network optimization engine 250 over anetwork 680 and to a client 630. In some instances the networkoptimization engine 250 can communicate with an instance of the networkoptimization engine 250′ executing on the client 630. The client 630 canbe any computer or client device described herein and the instance ofthe network optimization engine 250′ can be the network optimizationengine instance or client 250′ discussed in the above sections of thisdisclosure.

In some instances, network traffic can be routed or otherwisetransmitted according to a network transmission scheme. This networktransmission scheme can comprise various components including aprioritization scheme and a particular quality of service (QoS).Enhancement protocols used to prioritize network traffic such as themodified HWF2Q+ algorithm described above, can be modified to prioritizeparticular types of traffic. In some embodiments, this prioritizationcan be used to enforce a QoS requirement by fairly distributingbandwidth amongst multiple network streams. In one instance, theprioritization can include prioritizing highly compressed traffic. Inother embodiments, the prioritization can include prioritizingparticular network traffic classes such as traffic classified as minimumlatency traffic. Performing this level of prioritization can increasethe compression ratio for all highly compressed traffic and can reducean amount of memory used by low priority highly compressed traffic toretain highly compressed packet information until an acknowledgement isreceived. Furthermore, performing this level of prioritization canensure that accelerated traffic such as highly compressed acceleratedtraffic is optimally managed by the network optimization engine 250executing on the appliance 610. In some embodiments, this appliance 610can be a WAN acceleration appliance.

Illustrated in FIG. 7 is one embodiment of a method 700 for optimizingthe transmission of network traffic by applying a unique networktransmission scheme to highly compressed data packets. A networkoptimization engine 250 or traffic optimization engine can receive datapackets transmitted over one or more network streams (Step 710). Thenetwork optimization engine 250 then calculates a compression ratio foreach received data packet (Step 720) and determines whether thecalculated compression ratio exceeds a predetermined compression ratiothreshold (Step 730). When the network optimization engine determinesthat the packet's calculated compression ratio exceeds a predeterminedcompression ratio threshold, the network optimization engine classifiesthe packet as “highly compressed traffic” (Step 740) and transmits theclassified data packet according to a unique transmission scheme (Step750).

Further referring to FIG. 7, and in more detail, in some embodiments,the network optimization engine 250 receives data packets transmittedover a WAN pipe 620 or from a common link 650 (Step 710). The commonlink 650 can be a common router, a common pool of routers, a commonswitch, a common pool of switches or any other common appliance orserver. The received data packets can be received after they arecompressed and re-encrypted, or after they are decrypted and before theyare compressed. In other embodiments, the network optimization engine250 can receive the data packets after they are decrypted and compressedbut before they are re-encrypted.

Upon receiving data packets (Step 710), the network optimization enginecan calculate a compression ratio for each received data packet (Step720). In some embodiments, a compression ratio can be calculated by thenetwork optimization engine 250 during compression of the data withinthe network packet and stored as a parameter in the payload of thenetwork packet. The network optimization engine 250 can calculate thecompression ratio by storing the size of the data payload of the datapacket prior to compression of the data payload. After compressing thedata payload, the network optimization engine 250 can store the size ofthe compressed data payload. The compression ratio is the ratio of thesize of the uncompressed data payload to the size of the compressed datapayload. In some instances the network optimization engine 250 cancalculate this ratio and store it within the body of the data packet.When data packets are received after they have been compressed, thenetwork optimization engine 250 can analyze the data packet to determinewhether a compression ratio was stored in the data payload or body ofthe data packet. Upon failing to identify a compression ratio, thenetwork optimization engine 250 can analyze a QoS associated with thedata packet to determine the compression scheme used to compress thedata packet and calculate the compression ratio using the compressedsize of the data packet and the compression scheme. This process mayrequire the network optimization engine 250 to decompress the datapacket in order to obtain the uncompressed size of the data. Thus,calculating the compression ratio (Step 720) for each data packet cancomprise any of the following processes: analyzing the data packet toidentify a compression ratio stored within the data packet; compressingthe data packet according to a compression scheme identified within thedata packet and calculating the compression ratio based on theuncompressed and compressed data size; or using a compression schemeidentified within the data packet to estimate the compression ratio.While the above assumes that the data packet identifies its compressionscheme either in a QoS parameter or elsewhere in the body of the datapacket, in some instances the network optimization engine 250 may use acompression table to determine the compression scheme based oncharacteristics of the data packet.

The network optimization engine 250 can compare the compression ratiocalculated for each received network packet to a predeterminedcompression ratio threshold to determine whether or not the datapacket's compression ratio exceeds the predetermined compression ratiothreshold (Step 730). A predetermined compression ratio threshold can bea value hard-coded in the network optimization engine 250 or theappliance 610. In some embodiments, the predetermined compression ratiothreshold can be calculated by sampling a portion of data packets. Thisprocess can include calculating or determining the compression ratio foreach data packet in the sample, summing these compression ratios andcalculating an average compression ratio. The network optimizationengine 250 can then designate the calculated average compression ratioas the predetermined compression ratio threshold. In some embodiments,the network optimization engine 250 can use both the average compressionratio and a determination of the percentage of sampled data packets thatexceed the average compression ratio to determine the predeterminedcompression ratio threshold. When the network optimization engine 250determines that an insufficient number of data packets falls above orbelow the calculated average, the network optimization engine 250 cantweak the value of the calculate average to arrive at the compressionratio threshold. For example, if the network optimization engine 250determines that too many sampled network packets exceed the calculatedaverage, the network optimization engine 250 may designate thecompression ratio threshold as a value higher than the calculatedaverage.

The sample of data packets can be any of the following: data packetscomprising data generated by an application executing on a back-endserver 660 or other appliance in the network; a sample of data packetsreceived over a period of time; a group of data packets generated by aparticular session or originating from a particular IP address; a randomsampling of data packets from various sources sent over a period oftime; or data packets associated with a particular network class.

The predetermined compression ratio threshold can be a numerical valuerepresentative of a compression ratio. While the preferred embodimentcomprises determining whether the compression ratio for each data packetexceeds the predetermined compression ratio threshold, in otherembodiments the network optimization engine 250 randomly samples datapackets in a common network stream to periodically determine whether thecompression ratio for the entire network stream has exceeded thepredetermined compression ratio threshold. Periodic sampling of anetwork stream can include checking the compression ratio for datapackets after a predetermined period of time. For example, the networkoptimization engine 250 can sample the network stream and obtain arepresentative group of data packets to determine whether the averagecompression ratio has exceeded the compression ratio threshold. Thenetwork optimization engine 250 can then wait a period of time (i.e. 50seconds) and resample the network stream.

When the network optimization engine determines that a data packet orstream of data packets have been compressed such that their ratio ofcompression exceeds a predetermined ratio of compression threshold, thenetwork optimization engine can classify those packets as highlycompressed traffic (Step 740). Classifying one or more data packets as“highly compressed traffic” can include marking the data packets with anetwork classification or modifying a QoS parameter to indicate that thetraffic is highly compressed. A classification can be any classificationdescribed herein and in some instances can include marking the datapacket with a differentiated service code point.

Designating data packets as “highly compressed traffic” can furtherinclude assigning those packets a high priority. In some embodiments,one set of data packets can have a higher priority than another set ofdata packets. The low priority DBC traffic (or other highly compressedtraffic) can be identified and ascribed a high priority designation sothat the highly compressed portions of accelerated connections aretransmitted before other network traffic.

In some embodiments, classifying data packets as highly compressedtraffic can include sorting data packets according to whether or not adata packet has been marked with a highly compressed traffic marking.Still further embodiments can include ordering the sorted data packetsaccording to timestamps stored within a portion of the data packet.

Upon classifying network packets as highly compressed traffic, thenetwork optimization engine 250 can transmit the network packetsaccording to a unique transmission scheme (Step 750). This transmissionscheme can be a first transmission scheme that is different from othertransmission schemes associated with data packets not designated as ahighly compressed traffic. A transmission scheme can comprise aprioritization scheme and/or a particular QoS. In one embodiment,transmitting the data packets according to a unique transmission schemecan include transmitting the highly compressed data packets beforetransmitting other traffic. In another embodiment, the uniquetransmission scheme can include requiring data packets classified ashighly compressed traffic to be compressed and otherwise encoded beforeother non-highly compressed traffic and before being transmitted to anintermediary or destination network node. In still other embodiments,the unique transmission scheme can include prioritizing when the highlycompressed data packets are processed by additional components of thenetwork optimization engine 250 or WAN optimization scheme. Still otherembodiments include a transmission scheme that modifies the amount ofbandwidth or memory allocated to data packets classified as highlycompressed traffic. For example, the transmission scheme may includereducing the amount of memory available to highly compressed datapackets while increasing the amount of memory available to uncompresseddata packets not classified as highly compressed data packets.

In some embodiments, the method of receiving data packets andclassifying them as “highly compressed traffic” can be an iterativeprocess that repeats until there are no further data packets. Thetraffic shaping engine can resample and reanalyze previously analyzeddata packets and data packet streams to determine whether those packetsand streams still qualify for a “highly compressed traffic”classification. When the traffic shaping engine determines that apreviously classified data packet or stream of data packets no longerqualifies as “highly compressed traffic,” e.g. the compression ratio nolonger exceeds the predetermined threshold value, the traffic shapingengine can revoke the “highly compressed traffic” classification. Thus,the data packets are reclassified back to an original class. Revokingthe highly compressed traffic classification can include removing atraffic class marking that indicates a data packet is part of the highlycompressed traffic class, or modifying a QoS parameter indicating a datapacket is part of the highly compressed traffic class.

In some embodiments, transmission can include transmitting theclassified data packets according to the transmission scheme and inorder of when the packets were received. For example, the networkoptimization engine 250 may order the classified data packets accordingto a timestamp and retransmit them in a first-in-first-out fashion.

The above describes a method for prioritizing or handling highlycompressed traffic in a unique manner. Additional ways of optimizingnetwork traffic can include prioritizing or handling various classes ofnetwork traffic in a unique manner. An enhancement protocol such as themodified HWF2Q+ algorithm described above can be used to enforce a QoSrequirement by fairly distributing bandwidth amongst multiple networkstreams. In one instance, the prioritization can include prioritizingminimum latency traffic classes amongst themselves. Performing thislevel of prioritization can permit a maximum regulated rate with aminimum latency when compared to lower priority traffic.

Illustrated in FIG. 8 is a method 800 for prioritizing minimum latencytraffic. A network optimization engine 250 can receive data packetstransmitted over one or more network streams (Step 810), determinewhether the data packets comprise a traffic class marking (Step 820) andsort the data packets according to identified traffic class markings(Step 830). The network optimization engine can then transmit sorteddata packets have a traffic class marking according to a uniquetransmission scheme (Step 840).

Further referring to FIG. 8, and in more detail, in some embodiments,the network optimization engine 250 receives data packets transmittedover a WAN pipe 620 or from a common link 650 (Step 810). The commonlink 650 can be a common router, a common pool of routers, a commonswitch, a common pool of switches or any other common appliance orserver. The received data packets can be received after they arecompressed and re-encrypted, or after they are decrypted and before theyare compressed. In other embodiments, the network optimization engine250 can receive the data packets after they are decrypted and compressedbut before they are re-encrypted.

Upon receiving the data packets, the network optimization engine 250determines whether the data packets comprise a traffic class marking(Step 820). Determining a traffic class marking can include analyzingportions of the data packet, including the header, body and any otheraspect of the data payload to identify a marking indicative of a trafficclass. Traffic class markings can be any alpha-numeric mark thatindicates a class or classification. The classification can be anyclassification described herein or any value that can be used as afilter parameter. In some embodiments, the traffic class mark can be amark that indicates the data packet is part of a minimum latency class.This mark can be a differentiated service code point (DSCP) mark orsimilar indicia.

In some embodiments, the minimum latency traffic class can be a class oftraffic that must have a tight end-to-end delay bound. In otherembodiments, the minimum latency traffic class can be a class of trafficthat must be transmitted across the network with minimal delay.Applications that require minimum latency, such as VoIP or multimedianetwork traffic may require their traffic to be designated as minimumlatency traffic because those applications require real-time data toprovide an optimum user experience. Data generated by applications thatdo not typically require minimum latency may comprise portions of datathat must be generated real-time. For example, business applications(i.e. MICROSOFT WORD document or MICROSOFT POWER POINT document) havingembedded multimedia may require multimedia data to be transmitted withminimum latency while other aspects of the application data (i.e. text)may not require a minimum latency transmission. The method 800 describedherein can prioritize data on per application or per resource basis.Thus, while the business application may not have an administrativeclass that designates that data should be transmitted with a highpriority, the methods described herein can differentiate the lowpriority portions of the business application's data from the highpriority portions of the business application's data (i.e. themultimedia content). Other examples of data types and content that mayrequire a minimum latency transmission include audio, video, VoIP,certain graphics, rich graphics commands, localization information (i.e.GPS data) etc.

There can be various subclasses within a class of minimum latencytraffic. For example, multimedia streams can be divided into varioussub-streams such that different portions of the stream can betransmitted according to different transmission schemes. For example,audio within a multimedia stream can be transmitted according to atransmission scheme that prioritizes audio higher than the graphicsportion of the multimedia stream.

The method can, in some embodiments include determining whether datapackets or a stream of data packets comprises a traffic class marking byreviewing the following characteristics of the data packets or datastream: a QoS associated with the data; the type of data beingtransmitted; or the source of the data or the type of application thatgenerated the data packets. When data packets comprise any of the abovecharacteristics, the network optimization engine 250 can determine thatthe data packets should be transmitted according to a minimum latencytransmission scheme.

In other embodiments, the network optimization engine 250 can determinewhether packets comprise a traffic class marking by determining the typeof application that generated the data packets. A policy engine withinthe optimization engine 250 can look-up the application that generatedthe data packets and determine whether the data packets should beclassified as packets requiring a minimum latency transmission. In someembodiments, the indicia identified by the network optimization engine250 can indicate the application that generated the data of the datapacket and whether the application requires the data to be transmittedas part of the minimum latency traffic class.

Upon identifying network packets that comprise a traffic class marking,the network optimization engine 250 can sort the data packets accordingto identified traffic class markings (Step 830). The networkoptimization engine 250 can sort according to a particular trafficclass, or according to various traffic classes. For example, the networkoptimization engine 250 can sort the data packets into a group ofpackets that require a minimum latency transmission and those that donot. The network optimization engine 250 can also sort the data packetsinto groups of network classes wherein the minimum latency network classis one of many network classes.

Sorting the data packets can include generating a start list thatcomprises the received data packets. Creating a start list can includestoring each received data packet to a queue or storage array. The startlist, in some embodiments, can be a partially sorted list that is sortedby multiple filters. In one embodiment, the start list is first sortedby traffic class, e.g. sorted by “minimum latency traffic” and“non-minimum latency traffic.” Upon sorting the list by traffic class,the list can further be sorted by start times. These start times cancomprise timestamps of when each network packet was received by theappliance 610 or network optimization engine 250. By sorting such thatthe packets at the front of the queue are those corresponding to“minimum latency traffic” with the earliest start time; the “minimumlatency traffic” is transmitted over the network first and ahead of all“non-minimum latency traffic.” Accordingly, the end of the listcomprises “non-minimum latency traffic” sorted by start times ortimestamp values.

Upon sorting the data packets as minimum latency traffic, the networkoptimization engine 250 can transmit the network packets according to aunique transmission scheme (Step 840). This transmission scheme can be afirst transmission scheme that is different from other transmissionschemes associated with data packets not designated as minimum latencytraffic. A transmission scheme can comprise a prioritization schemeand/or a particular QoS. In one embodiment, transmitting the datapackets according to a unique transmission scheme can includeprioritizing the minimum latency traffic ahead of non-minimum latencytraffic. In this embodiment, the network optimization engine 250transmits the data packets identified as having a minimum latencytraffic class mark or identifier before it transmits other data packets.The transmission scheme associated with those other data packets isdifferent and does not have the same prioritization scheme as the schemeincluded in the transmission scheme for the minimum latency trafficclass.

In another embodiment, the unique transmission scheme can includerequiring data packets classified as minimum latency traffic to becompressed and otherwise encoded before other non-minimum latencytraffic and before being transmitted to an intermediary or destinationnetwork node. In still other embodiments, the unique transmission schemecan include prioritizing when the minimum latency data packets areprocessed by additional components of the network optimization engine250 or WAN optimization scheme.

EXAMPLE 1

A traffic shaping engine receives data packets obtained by an optimizingappliance. The traffic shaping engine reviews a DSCP mark or otheridentifying mark on the packets' payload to determine a QoS or classassociated with the network packet. Upon determining a QoS andsubsequently whether the data packet belongs to a “minimum-latency”traffic class, the traffic shaping engine sorts the queue into trafficidentified as requiring a “minimum-latency” and traffic identified asnot requiring a “minimum-latency.” For example, VoIP packets transmittedby an enterprise exchange are tagged as “minimum-latency” while VoIPpackets transmitted by SKYPE are tagged as “non-minimum-latency.”Uponsorting the queue into “minimum-latency” and “non-minimum latency”traffic, the traffic shaping engine further sorts the queue segments bya timestamp value associated with each data packet. In some instances,the sort uses a first-in-first-out (FIFO) method of placing thosepackets with the oldest timestamp at the beginning of the queue. Thus,the first data packets in the queue are those packets identified asbeing “minimum-latency” traffic having the earliest timestamp.

EXAMPLE 2

In one example, audio of a multimedia stream can be transmitted on aseparate stream having a high QoS or high service priority level. Eachsub-stream can be prioritized according to a priority level determinedby the application that generates the data or the data type of the data.An appliance executing a network optimization engine that provides WANoptimization can be used to auto-detect applications that requireminimum-latency transmission. Upon automatically detecting theseapplications and thereby the data generated by these applications, thenetwork optimization engine can provision a separate TCP stream that canbe used to deliver the data over a network channel according to a highpriority or enhanced QoS. For example, the appliance can provision aseparate TCP stream to transmit audio data at a high priority servicelevel. This audio data can be extracted from multimedia data subsequentto identifying that the multimedia data requires a high service level.In some instances, the traffic shaping priorities can be based on auser-group, application-group, service-type, user-location or otherattribute. Thus, traffic shaping can occur on a per-user orper-application basis.

While various embodiments of the methods and systems have beendescribed, these embodiments are exemplary and in no way limit the scopeof the described methods or systems. Those having skill in the relevantart can effect changes to form and details of the described methods andsystems without departing from the broadest scope of the describedmethods and systems. Thus, the scope of the methods and systemsdescribed herein should not be limited by any of the exemplaryembodiments and should be defined in accordance with the accompanyingclaims and their equivalents.

The invention claimed is:
 1. A method for optimizing transmission ofnetwork traffic, the method comprising: receiving, by a networkoptimization engine executing on an appliance, data packets transmittedover a network; analyzing, by the network optimization engine, each ofthe received data packets to calculate a compression ratio for each datapacket; determining, by the network optimization engine, a compressionratio threshold based on a sampling of the compression ratios of aportion the received data packets; classifying, by the networkoptimization engine, a first set of the received data packets having acompression ratio exceeding the compression ratio threshold as highlycompressed traffic and a second set of the received data packets havinga compression ratio not exceeding the compression ratio threshold asnon-highly compressed traffic; transmitting the first set of thereceived data packets classified as highly compressed traffic accordingto a first transmission scheme; and transmitting the second set of thereceived data packets classified as non-highly compressed trafficaccording to a second transmission scheme, the first transmission schemediffering the second transmission scheme.
 2. The method of claim 1,wherein receiving the data packets transmitted over the network furthercomprises receiving the data packets from a common output link.
 3. Themethod of claim 2, wherein receiving the data packets transmitted fromthe common output link further comprises receiving the data packets fromone of a common router and a common switch.
 4. The method of claim 2,wherein receiving the data packets transmitted from the common outputlink further comprises receiving the data packets over a wide areanetwork (WAN) pipe.
 5. The method of claim 1, wherein determining acompression ratio threshold based on the sampling of the compressionratios of a portion the received data packets comprises: calculating anaverage compression ratio from the compression ratios of the receiveddata packets in the portion; and storing the average compression ratioas the compression ratio threshold.
 6. The method of claim 1, whereincalculating the compression ratio for each of the received data packetscomprises calculating the compression ratio for data packets comprisingdata generated by a first application.
 7. The method of claim 1, whereinclassifying the first set of the received data packets as highlycompressed traffic further comprises marking the data packets in thefirst set as part of a highly compressed traffic class.
 8. The method ofclaim 1, wherein classifying the first set of the received data packetsas highly compressed traffic further comprises modifying one or morecharacteristics of a QoS parameter of the data packets in the first set.9. The method of claim 1, further comprising: determining, by thenetwork optimization engine subsequent to receiving the data packets,whether one or more of the received data packets comprise a markidentifying a highly compressed traffic class; and removing the one ormore received data packets from the highly compressed traffic class bymodifying the one or more of the received data packets to remove themark identifying the highly compressed traffic class if the compressionratio of the one or more of the received data packets does not exceedthe compression ratio threshold.
 10. The method of claim 1, furthercomprising ordering, by the network optimization engine prior totransmission, the received data packets based in part on a timestampvalue associated with each data packet.
 11. The method of claim 1,wherein determining the compression ratio threshold based on thesampling of the compression ratios of the portion the received datapackets comprises sampling the compression ratios of a representativeportion of the received data packets to determine whether an averagecompression ratio of the representative portion of the received datapackets differs from a current compression ratio threshold.
 12. Themethod of claim 1, further comprising: calculating, subsequent to thetransmission of at least one of the received data packets according tothe highly compressed traffic classification, a new compression ratiothreshold by sampling the compression ratios of a second portion of thereceived data packets; and reclassifying at least one data packet in thefirst set of the received data packets classified as highly compressedtraffic as non-highly compressed traffic or at least one data packet inthe second set of the received data packets classified as non-highlycompressed as highly compressed traffic based on the new compressionratio threshold.
 13. The method of claim 1, further comprising sortingthe first set of the received data packets and the second set ofreceived data packets in a queue for transmission according to thehighly compressed traffic classification, where data packets in thefirst set of the received data packets classified as highly compressedtraffic receive a higher priority for transmission in the queue thandata packets in the second set of the received data packets classifiedas non-highly compressed traffic.
 14. The method of claim 1, furthercomprising reducing an amount of memory allocated to the first set ofthe received data packets and increasing an amount of memory allocatedto the second set of the received data packets.
 15. A system foroptimizing transmission of network traffic, the system comprising: anetwork optimization engine executing on a network appliance wherein thenetwork optimization engine receives data packets transmitted over anetwork, the network optimization engine: analyzing each of the receiveddata packets to calculate a compression ratio for each data packet;determining a compression ratio threshold based on a sampling of thecompression ratios of a portion the received data packets; classifying afirst set of the received data packets having a compression ratioexceeding the compression ratio threshold as highly compressed trafficand a second set of the received data packets having a compression rationot exceeding the compression ratio threshold as non-highly compressedtraffic; transmitting the first set of the received data packetsclassified as highly compressed traffic according to a firsttransmission scheme; and transmitting the second set of the receiveddata packets classified as non-highly compressed traffic according to asecond transmission scheme, the first transmission scheme differing thesecond transmission scheme.
 16. The system of claim 15, wherein thenetwork optimization engine receives the data packets from a commonoutput link.
 17. The system of claim 16, wherein the common output linkcomprises one of a common router and a common switch.
 18. The system ofclaim 15, wherein the network optimization engine receives the datapackets over a wide area network (WAN) pipe.
 19. The system of claim 15,wherein determining a compression ratio threshold based on the samplingof the compression ratios of a portion the received data packetscomprises: calculating an average compression ratio from the compressionratios of the received data packets in the portion; and storing theaverage compression ratio as the compression ratio threshold.
 20. Thesystem of claim 15, wherein calculating the compression ratio for eachof the received data packets comprises calculating the compression ratiofor data packets comprising data generated by a first application. 21.The system of claim 15, wherein classifying the first set of thereceived data packets as highly compressed traffic comprises marking thedata packets in the first set as part of a highly compressed trafficclass.
 22. The system of claim 15, wherein classifying the first set ofthe received data packets as highly compressed traffic comprisesmodifying one or more characteristics of a QoS parameter of the datapackets in the first set.
 23. The system of claim 15, wherein thenetwork optimization engine further: determines, subsequent to receivingdata packets, whether one or more of the received data packets comprisea mark identifying a highly compressed traffic class; and removes theone or more received data packets from the highly compressed trafficclass by modifying the one or more of the received data packets toremove the mark identifying the highly compressed traffic class if thecompression ratio of the one or more of the received data packets doesnot exceed the compression ratio threshold.
 24. The system of claim 15,wherein the network optimization engine orders the received data packetsprior to transmission based in part on a timestamp values associatedwith each data packet.
 25. The system of claim 15, wherein determiningthe compression ratio threshold based on the sampling of the compressionratios of the portion the received data packets comprises sampling thecompression ratios of a representative portion of the received datapackets to determine whether an average compression ratio of therepresentative portion of the received data packets differs from acurrent compression ratio threshold.
 26. The system of claim 15, whereinthe network optimization engine: calculates, subsequent to thetransmission of at least one of the received data packets according tothe highly compressed traffic classification, a new compression ratiothreshold by sampling the compression ratios of a second portion of thereceived data packets; and reclassifies at least one data packet in thefirst set of the received data packets classified as highly compressedtraffic as non-highly compressed traffic or at least one data packet inthe second set of the received data packets classified as non-highlycompressed as highly compressed traffic based on the new compressionratio threshold.
 27. The system of claim 15, wherein the networkoptimization engine sorts the first set of the received data packets andthe second set of received data packets in a queue for transmissionaccording to the highly compressed traffic classification, where datapackets in the first set of the received data packets classified ashighly compressed traffic receive a higher priority for transmission inthe queue than data packets in the second set of the received datapackets classified as non-highly compressed traffic.
 28. The system ofclaim 15, wherein the network optimization engine reduces an amount ofmemory allocated to the first set of the received data packets andincreasing an amount of memory allocated to the second set of thereceived data packets.